The package in bionic-proposed indeed fix the issue:

root@corosync-verification:~# dpkg -l | grep corosync
ii  corosync                       2.4.3-0ubuntu1.3                    amd64        cluster engine daemon and utilities
ii  libcorosync-common4:amd64      2.4.3-0ubuntu1.3                    amd64        cluster engine common library
root@corosync-verification:~# corosync-blackbox
Dumping the contents of /var/lib/corosync/fdata
[debug] shm size:8392704; real_size:8392704; rb->word_size:2098176
[debug] read total of: 8392724
Ringbuffer: 
 ->NORMAL
 ->write_pt [2866]
 ->read_pt [0]
 ->size [2098176 words]
 =>free [8381236 bytes]
 =>used [11464 bytes]
debug   Nov 10 15:51:24 totempg_waiting_trans_ack_cb(286):14: waiting_trans_ack changed to 1
debug   Nov 10 15:51:24 totemsrp_initialize(900):14: Token Timeout (3000 ms) retransmit timeout (294 ms)
debug   Nov 10 15:51:24 totemsrp_initialize(903):14: token hold (225 ms) retransmits before loss (10 retrans)
debug   Nov 10 15:51:24 totemsrp_initialize(910):14: join (50 ms) send_join (0 ms) consensus (3600 ms) merge (200 ms)
debug   Nov 10 15:51:24 totemsrp_initialize(913):14: downcheck (1000 ms) fail to recv const (2500 msgs)
debug   Nov 10 15:51:24 totemsrp_initialize(915):14: seqno unchanged const (30 rotations) Maximum network MTU 1401
debug   Nov 10 15:51:24 totemsrp_initialize(919):14: window size per rotation (50 messages) maximum messages per rotation (17 messages)
debug   Nov 10 15:51:24 totemsrp_initialize(923):14: missed count const (5 messages)
debug   Nov 10 15:51:24 totemsrp_initialize(926):14: send threads (0 threads)
debug   Nov 10 15:51:24 totemsrp_initialize(929):14: RRP token expired timeout (294 ms)
debug   Nov 10 15:51:24 totemsrp_initialize(932):14: RRP token problem counter (2000 ms)
debug   Nov 10 15:51:24 totemsrp_initialize(935):14: RRP threshold (10 problem count)
debug   Nov 10 15:51:24 totemsrp_initialize(938):14: RRP multicast threshold (100 problem count)
debug   Nov 10 15:51:24 totemsrp_initialize(941):14: RRP automatic recovery check timeout (1000 ms)
debug   Nov 10 15:51:24 totemsrp_initialize(943):14: RRP mode set to none.
debug   Nov 10 15:51:24 totemsrp_initialize(946):14: heartbeat_failures_allowed (0)
debug   Nov 10 15:51:24 totemsrp_initialize(948):14: max_network_delay (50 ms)
debug   Nov 10 15:51:24 totemsrp_initialize(971):14: HeartBeat is Disabled. To enable set heartbeat_failures_allowed > 0
notice  Nov 10 15:51:24 totemnet_instance_initialize(248):14: Initializing transport (UDP/IP Multicast).
notice  Nov 10 15:51:24 init_nss(688):14: Initializing transmit/receive security (NSS) crypto: none hash: none
debug   Nov 10 15:51:24 totemudp_build_sockets_ip(923):14: Receive multicast socket recv buffer size (320000 bytes).
debug   Nov 10 15:51:24 totemudp_build_sockets_ip(929):14: Transmit multicast socket send buffer size (320000 bytes).
debug   Nov 10 15:51:24 totemudp_build_sockets_ip(935):14: Local receive multicast loop socket recv buffer size (320000 bytes).
debug   Nov 10 15:51:24 totemudp_build_sockets_ip(941):14: Local transmit multicast loop socket send buffer size (320000 bytes).
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 2 for FD 8
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 3 for FD 9
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 4 for FD 12
notice  Nov 10 15:51:24 timer_function_netif_check_timeout(669):14: The network interface [127.0.0.1] is now up.
debug   Nov 10 15:51:24 main_iface_change_fn(5101):14: Created or loaded sequence id 0.127.0.0.1 for this ring.
info    Nov 10 15:51:24 qb_ipcs_us_publish(537):9: server name: cmap
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 5 for FD 13
info    Nov 10 15:51:24 qb_ipcs_us_publish(537):9: server name: cfg
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 6 for FD 14
info    Nov 10 15:51:24 qb_ipcs_us_publish(537):9: server name: cpg
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 7 for FD 15
info    Nov 10 15:51:24 qb_ipcs_us_publish(537):9: server name: votequorum
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 8 for FD 16
info    Nov 10 15:51:24 qb_ipcs_us_publish(537):9: server name: quorum
trace   Nov 10 15:51:24 qb_loop_poll_add(368):9: grown poll array to 9 for FD 17
debug   Nov 10 15:51:24 memb_state_gather_enter(2222):14: entering GATHER state from 15(interface change).
debug   Nov 10 15:51:24 memb_state_commit_token_create(3274):14: Creating commit token because I am the rep.
debug   Nov 10 15:51:24 old_ring_state_save(1605):14: Saving state aru 0 high seq received 0
debug   Nov 10 15:51:24 memb_state_commit_enter(2271):14: entering COMMIT state.
debug   Nov 10 15:51:24 message_handler_memb_commit_token(4929):14: got commit token
debug   Nov 10 15:51:24 memb_state_recovery_enter(2308):14: entering RECOVERY state.
debug   Nov 10 15:51:24 memb_state_recovery_enter(2354):14: position [0] member 127.0.0.1:
debug   Nov 10 15:51:24 memb_state_recovery_enter(2358):14: previous ring seq 0 rep 127.0.0.1
debug   Nov 10 15:51:24 memb_state_recovery_enter(2364):14: aru 0 high delivered 0 received flag 1
debug   Nov 10 15:51:24 memb_state_recovery_enter(2462):14: Did not need to originate any messages in recovery.
debug   Nov 10 15:51:24 message_handler_memb_commit_token(4929):14: got commit token
debug   Nov 10 15:51:24 message_handler_memb_commit_token(4994):14: Sending initial ORF token
trace   Nov 10 15:51:24 totemsrp_mcast(2547):14: mcasted message added to pending queue
debug   Nov 10 15:51:24 message_handler_orf_token(4176):14: token retrans flag is 0 my set retrans flag0 retrans queue empty 1 count 0, aru 0
debug   Nov 10 15:51:24 message_handler_orf_token(4187):14: install seq 0 aru 0 high seq received 0
debug   Nov 10 15:51:24 message_handler_orf_token(4176):14: token retrans flag is 0 my set retrans flag0 retrans queue empty 1 count 1, aru 0
debug   Nov 10 15:51:24 message_handler_orf_token(4187):14: install seq 0 aru 0 high seq received 0
debug   Nov 10 15:51:24 message_handler_orf_token(4176):14: token retrans flag is 0 my set retrans flag0 retrans queue empty 1 count 2, aru 0
debug   Nov 10 15:51:24 message_handler_orf_token(4187):14: install seq 0 aru 0 high seq received 0
debug   Nov 10 15:51:24 message_handler_orf_token(4176):14: token retrans flag is 0 my set retrans flag0 retrans queue empty 1 count 3, aru 0
debug   Nov 10 15:51:24 message_handler_orf_token(4187):14: install seq 0 aru 0 high seq received 0
debug   Nov 10 15:51:24 message_handler_orf_token(4206):14: retrans flag count 4 token aru 0 install seq 0 aru 0 0
debug   Nov 10 15:51:24 old_ring_state_reset(1621):14: Resetting old ring state
debug   Nov 10 15:51:24 deliver_messages_from_recovery_to_regular(1852):14: recovery to regular 1-0
trace   Nov 10 15:51:24 memb_state_operational_enter(1943):14: Delivering to app 1 to 0
debug   Nov 10 15:51:24 totempg_waiting_trans_ack_cb(286):14: waiting_trans_ack changed to 1
debug   Nov 10 15:51:24 memb_state_operational_enter(2128):14: entering OPERATIONAL state.
notice  Nov 10 15:51:24 memb_state_operational_enter(2134):14: A new membership (127.0.0.1:4) was formed. Members joined: 2130706433
trace   Nov 10 15:51:24 totemsrp_mcast(2547):14: mcasted message added to pending queue
trace   Nov 10 15:51:24 messages_deliver_to_app(4278):14: Delivering 0 to 2
trace   Nov 10 15:51:24 messages_deliver_to_app(4347):14: Delivering MCAST message with seq 1 to pending delivery queue
trace   Nov 10 15:51:24 messages_deliver_to_app(4347):14: Delivering MCAST message with seq 2 to pending delivery queue
trace   Nov 10 15:51:24 totemsrp_mcast(2547):14: mcasted message added to pending queue
trace   Nov 10 15:51:24 messages_deliver_to_app(4278):14: Delivering 2 to 3
trace   Nov 10 15:51:24 messages_deliver_to_app(4347):14: Delivering MCAST message with seq 3 to pending delivery queue
trace   Nov 10 15:51:24 totemsrp_mcast(2547):14: mcasted message added to pending queue
trace   Nov 10 15:51:24 totemsrp_mcast(2547):14: mcasted message added to pending queue
trace   Nov 10 15:51:24 messages_free(2676):14: releasing messages up to and including 2
trace   Nov 10 15:51:24 messages_deliver_to_app(4278):14: Delivering 3 to 5
trace   Nov 10 15:51:24 messages_deliver_to_app(4347):14: Delivering MCAST message with seq 4 to pending delivery queue
trace   Nov 10 15:51:24 messages_deliver_to_app(4347):14: Delivering MCAST message with seq 5 to pending delivery queue
trace   Nov 10 15:51:24 totemsrp_mcast(2547):14: mcasted message added to pending queue
trace   Nov 10 15:51:24 messages_free(2676):14: releasing messages up to and including 3
trace   Nov 10 15:51:24 messages_deliver_to_app(4278):14: Delivering 5 to 6
trace   Nov 10 15:51:24 messages_deliver_to_app(4347):14: Delivering MCAST message with seq 6 to pending delivery queue
debug   Nov 10 15:51:24 totempg_waiting_trans_ack_cb(286):14: waiting_trans_ack changed to 0
trace   Nov 10 15:51:24 messages_free(2676):14: releasing messages up to and including 5
trace   Nov 10 15:51:24 messages_free(2676):14: releasing messages up to and including 6
trace   Nov 10 15:51:49 qb_loop_poll_add(368):9: grown poll array to 10 for FD 18
debug   Nov 10 15:51:49 handle_new_connection(647):9: IPC credentials authenticated (1382-1678-18)
debug   Nov 10 15:51:49 qb_ipcs_shm_connect(285):9: connecting to client [1678]
debug   Nov 10 15:51:49 qb_rb_open_2(238):9: shm size:1048589; real_size:1052672; rb->word_size:263168
debug   Nov 10 15:51:49 qb_rb_open_2(238):9: shm size:1048589; real_size:1052672; rb->word_size:263168
debug   Nov 10 15:51:49 qb_rb_open_2(238):9: shm size:1048589; real_size:1052672; rb->word_size:263168
trace   Nov 10 15:51:49 qb_loop_poll_add(368):9: grown poll array to 11 for FD 18
debug   Nov 10 15:51:49 qb_ipcs_dispatch_connection_request(759):9: HUP conn (1382-1678-18)
debug   Nov 10 15:51:49 qb_ipcs_disconnect(606):9: qb_ipcs_disconnect(1382-1678-18) state:2
trace   Nov 10 15:51:49 qb_rb_close(290):9: ENTERING qb_rb_close()
debug   Nov 10 15:51:49 qb_rb_close_helper(337):9: Free'ing ringbuffer: /dev/shm/qb-cmap-response-1382-1678-18-header
trace   Nov 10 15:51:49 my_posix_sem_destroy(91):9: ENTERING my_posix_sem_destroy()
trace   Nov 10 15:51:49 qb_rb_close(290):9: ENTERING qb_rb_close()
debug   Nov 10 15:51:49 qb_rb_close_helper(337):9: Free'ing ringbuffer: /dev/shm/qb-cmap-event-1382-1678-18-header
trace   Nov 10 15:51:49 my_posix_sem_destroy(91):9: ENTERING my_posix_sem_destroy()
trace   Nov 10 15:51:49 qb_rb_close(290):9: ENTERING qb_rb_close()
debug   Nov 10 15:51:49 qb_rb_close_helper(337):9: Free'ing ringbuffer: /dev/shm/qb-cmap-request-1382-1678-18-header
trace   Nov 10 15:51:49 my_posix_sem_destroy(91):9: ENTERING my_posix_sem_destroy()
debug   Nov 10 15:51:49 handle_new_connection(647):9: IPC credentials authenticated (1382-1680-18)
debug   Nov 10 15:51:49 qb_ipcs_shm_connect(285):9: connecting to client [1680]
debug   Nov 10 15:51:49 qb_rb_open_2(238):9: shm size:1048589; real_size:1052672; rb->word_size:263168
debug   Nov 10 15:51:49 qb_rb_open_2(238):9: shm size:1048589; real_size:1052672; rb->word_size:263168
debug   Nov 10 15:51:49 qb_rb_open_2(238):9: shm size:1048589; real_size:1052672; rb->word_size:263168
ERROR: qb_rb_chunk_read failed: Connection timed out
[trace] ENTERING qb_rb_close()
[debug] Free'ing ringbuffer: /dev/shm/qb-create_from_file-header
root@corosync-verification:~# echo $?
0
root@corosync-verification:~#