Hi Joshua,

the problem exists since ubuntu17.10. (slapd-2.4.45+dfsg-1ubuntu1). Dhparam created with openssl without the '-dsaparam' work fine.
 
Here is a full log take while trying to add the dhparam with '-dsaparam'.

Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: slap_listener_activate(10):
Okt 19 09:34:55 dc01 slapd[7928]: >>> slap_listener(ldapi:///)
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 busy
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=0 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: listen=10, new connection on 14
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:  14r
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: read active on 14
Okt 19 09:34:55 dc01 slapd[7928]: daemon: added 14r (active) listener=(nil)
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: connection_get(14)
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: connection_get(14): got connid=1111
Okt 19 09:34:55 dc01 slapd[7928]: connection_read(14): checking for input on id=1111
Okt 19 09:34:55 dc01 slapd[7928]: op tag 0x60, time 1508398495
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=0 do_bind
Okt 19 09:34:55 dc01 slapd[7928]: >>> dnPrettyNormal: <>
Okt 19 09:34:55 dc01 slapd[7928]: <<< dnPrettyNormal: <>, <>
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=0 BIND dn="" method=163
Okt 19 09:34:55 dc01 slapd[7928]: do_bind: dn () SASL mech EXTERNAL
Okt 19 09:34:55 dc01 slapd[7928]: ==> sasl_bind: dn="" mech=EXTERNAL datalen=0
Okt 19 09:34:55 dc01 slapd[7928]: SASL Canonicalize [conn=1111]: authcid="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth"
Okt 19 09:34:55 dc01 slapd[7928]: slap_sasl_getdn: conn 1111 id=gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth [len=55]
Okt 19 09:34:55 dc01 slapd[7928]: ==>slap_sasl2dn: converting SASL name gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth to a DN
Okt 19 09:34:55 dc01 slapd[7928]: <==slap_sasl2dn: Converted SASL name to <nothing>
Okt 19 09:34:55 dc01 slapd[7928]: SASL Canonicalize [conn=1111]: slapAuthcDN="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth"
Okt 19 09:34:55 dc01 slapd[7928]: SASL proxy authorize [conn=1111]: authcid="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" authzid="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth"
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=0 BIND authcid="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" authzid="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth"
Okt 19 09:34:55 dc01 slapd[7928]: SASL Authorize [conn=1111]:  proxy authorization allowed authzDN=""
Okt 19 09:34:55 dc01 slapd[7928]: send_ldap_sasl: err=0 len=-1
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=0 BIND dn="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" mech=EXTERNAL sasl_ssf=0 ssf=71
Okt 19 09:34:55 dc01 slapd[7928]: do_bind: SASL/EXTERNAL bind: dn="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" sasl_ssf=0
Okt 19 09:34:55 dc01 slapd[7928]: send_ldap_response: msgid=1 tag=97 err=0
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=0 RESULT tag=97 err=0 text=
Okt 19 09:34:55 dc01 slapd[7928]: <== slap_sasl_bind: rc=0
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 fd=14 ACCEPT from PATH=/var/run/slapd/ldapi (PATH=/var/run/slapd/ldapi)
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:  14r
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: read active on 14
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: connection_get(14)
Okt 19 09:34:55 dc01 slapd[7928]: connection_get(14): got connid=1111
Okt 19 09:34:55 dc01 slapd[7928]: connection_read(14): checking for input on id=1111
Okt 19 09:34:55 dc01 slapd[7928]: op tag 0x66, time 1508398495
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=1 do_modify
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=1 do_modify: dn (cn=config)
Okt 19 09:34:55 dc01 slapd[7928]: >>> dnPrettyNormal: <cn=config>
Okt 19 09:34:55 dc01 slapd[7928]: <<< dnPrettyNormal: <cn=config>, <cn=config>
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=1 modifications:
Okt 19 09:34:55 dc01 slapd[7928]:         replace: olcTLSDHParamFile
Okt 19 09:34:55 dc01 slapd[7928]:                 one value, length 21
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=1 MOD dn="cn=config"
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=1 MOD attr=olcTLSDHParamFile
Okt 19 09:34:55 dc01 slapd[7928]: => access_allowed: result not in cache (olcTLSDHParamFile)
Okt 19 09:34:55 dc01 slapd[7928]: => access_allowed: delete access to "cn=config" "olcTLSDHParamFile" requested
Okt 19 09:34:55 dc01 slapd[7928]: => acl_get: [1] attr olcTLSDHParamFile
Okt 19 09:34:55 dc01 slapd[7928]: => acl_mask: access to entry "cn=config", attr "olcTLSDHParamFile" requested
Okt 19 09:34:55 dc01 slapd[7928]: => acl_mask: to all values by "gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth", (=0)
Okt 19 09:34:55 dc01 slapd[7928]: <= check a_dn_pat: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
Okt 19 09:34:55 dc01 slapd[7928]: <= check a_authz.sai_ssf: ACL 71 > OP 71
Okt 19 09:34:55 dc01 slapd[7928]: <= acl_mask: [1] applying manage(=mwrscxd) (stop)
Okt 19 09:34:55 dc01 slapd[7928]: <= acl_mask: [1] mask: manage(=mwrscxd)
Okt 19 09:34:55 dc01 slapd[7928]: => slap_access_allowed: delete access granted by manage(=mwrscxd)
Okt 19 09:34:55 dc01 slapd[7928]: => access_allowed: delete access granted by manage(=mwrscxd)
Okt 19 09:34:55 dc01 slapd[7928]: => access_allowed: result not in cache (olcTLSDHParamFile)
Okt 19 09:34:55 dc01 slapd[7928]: => access_allowed: add access to "cn=config" "olcTLSDHParamFile" requested
Okt 19 09:34:55 dc01 slapd[7928]: => acl_get: [1] attr olcTLSDHParamFile
Okt 19 09:34:55 dc01 slapd[7928]: => acl_mask: access to entry "cn=config", attr "olcTLSDHParamFile" requested
Okt 19 09:34:55 dc01 slapd[7928]: => acl_mask: to value by "gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth", (=0)
Okt 19 09:34:55 dc01 slapd[7928]: <= check a_dn_pat: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
Okt 19 09:34:55 dc01 slapd[7928]: <= check a_authz.sai_ssf: ACL 71 > OP 71
Okt 19 09:34:55 dc01 slapd[7928]: <= acl_mask: [1] applying manage(=mwrscxd) (stop)
Okt 19 09:34:55 dc01 slapd[7928]: <= acl_mask: [1] mask: manage(=mwrscxd)
Okt 19 09:34:55 dc01 slapd[7928]: => slap_access_allowed: add access granted by manage(=mwrscxd)
Okt 19 09:34:55 dc01 slapd[7928]: => access_allowed: add access granted by manage(=mwrscxd)
Okt 19 09:34:55 dc01 slapd[7928]: slap_queue_csn: queueing 0x7fa448108610 20171019073455.596594Z#000000#000#000000
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_required entry (cn=config), objectClass "olcGlobal"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "objectClass"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "cn"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcArgsFile"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcIdleTimeout"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcPidFile"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcThreads"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcToolThreads"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "structuralObjectClass"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "entryUUID"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "creatorsName"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "createTimestamp"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSCACertificateFile"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSCertificateFile"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSCertificateKeyFile"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSCipherSuite"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSProtocolMin"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSVerifyClient"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcLogLevel"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "olcTLSDHParamFile"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "entryCSN"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "modifiersName"
Okt 19 09:34:55 dc01 slapd[7928]: oc_check_allowed type "modifyTimestamp"
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: send_ldap_result: conn=1111 op=1 p=3
Okt 19 09:34:55 dc01 slapd[7928]: send_ldap_result: err=80 matched="" text=""
Okt 19 09:34:55 dc01 slapd[7928]: send_ldap_response: msgid=2 tag=103 err=80
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=1 RESULT tag=103 err=80 text=
Okt 19 09:34:55 dc01 slapd[7928]: slap_graduate_commit_csn: removing 0x7fa448108610 20171019073455.596594Z#000000#000#000000
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:  14r
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: read active on 14
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: connection_get(14)
Okt 19 09:34:55 dc01 slapd[7928]: connection_get(14): got connid=1111
Okt 19 09:34:55 dc01 slapd[7928]: connection_read(14): checking for input on id=1111
Okt 19 09:34:55 dc01 slapd[7928]: op tag 0x42, time 1508398495
Okt 19 09:34:55 dc01 slapd[7928]: ber_get_next on fd 14 failed errno=0 (Success)
Okt 19 09:34:55 dc01 slapd[7928]: connection_read(14): input error=-2 id=1111, closing.
Okt 19 09:34:55 dc01 slapd[7928]: connection_closing: readying conn=1111 sd=14 for close
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on 1 descriptor
Okt 19 09:34:55 dc01 slapd[7928]: daemon: activity on:
Okt 19 09:34:55 dc01 slapd[7928]:
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=8 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=9 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=10 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=11 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: daemon: epoll: listen=12 active_threads=1 tvp=zero
Okt 19 09:34:55 dc01 slapd[7928]: connection_close: deferring conn=1111 sd=14
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=2 do_unbind
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 op=2 UNBIND
Okt 19 09:34:55 dc01 slapd[7928]: connection_resched: attempting closing conn=1111 sd=14
Okt 19 09:34:55 dc01 slapd[7928]: connection_close: conn=1111 sd=14
Okt 19 09:34:55 dc01 slapd[7928]: daemon: removing 14
Okt 19 09:34:55 dc01 slapd[7928]: conn=1111 fd=14 closed

Best regards,
Thorsten