Comment 4 for bug 1271559

I've been seeing similar symptoms in 2.6.3 and tried Liam's patch, but it did not help.

Network or server failure. Please check your Internet connection to catalog.sparkpa.org and choose Retry Network. If you need to enter Offline Mode, choose Ignore Errors in this and subsequent dialogs. If you believe this error is due to a bug in Evergreen and not network problems, please contact your help desk or friendly Evergreen administrators, and give them this information:
method=open-ils.search.z3950.search_class
params=["authtokenscrubbed",{"service_array":["accesspa","bpl","EGIN","loc"],"username_array":["","","",""],"password_array":["","","",""],"limit":3,"offset":0,"search":{"isbn":"9780547858197"},"service":["accesspa","bpl","EGIN","loc"],"username":["","","",""],"password":["","","",""]}]
THROWN:
{"fileName":"oils://remote/js/dojo/dojo/dojo.js","lineNumber":31}
STATUS:

So, the same query can work some times and not at others. Log activity is nearly identical between the two, but here's the part that changes:

WORKING QUERY:
z3950: connecting to server lx2.loc.gov:210:LCDB as
z3950: query => @attr 1=7 @attr 4=6 @attr 5=1 "9780547858197" z3950: search [@attr 1=7 @attr 4=6 @attr 5=1 "9780547858197" ] took 0 seconds
z3950: using record format 'F' and transmission format 'usmarc'
z3950: 'bpl' search returned 1 hits
z3950: fetching record 0
z3950: using record format 'F' and transmission format 'usmarc'
z3950: 'EGIN' search returned 0 hits
z3950: using record format 'F' and transmission format 'usmarc'
z3950: 'accesspa' search returned 1 hits
z3950: fetching record 0
z3950: using record format 'FI' and transmission format 'usmarc'
z3950: 'loc' search returned 1 hits
z3950: fetching record 0
Message processing duration: 6.254

BROKEN QUERY:
z3950: connecting to server lx2.loc.gov:210:LCDB as
z3950: query => @attr 1=7 @attr 4=6 @attr 5=1 "9780547858197"
z3950: search [@attr 1=7 @attr 4=6 @attr 5=1 "9780547858197" ] took 0 seconds
z3950: using record format 'F' and transmission format 'usmarc'
z3950: 'bpl' search returned 1 hits
z3950: fetching record 0
z3950: using record format 'F' and transmission format 'usmarc'
z3950: 'accesspa' search returned 1 hits
z3950: fetching record 0
z3950: using record format 'FI' and transmission format 'usmarc'
z3950: 'loc' search returned 1 hits
z3950: fetching record 0
z3950: using record format 'F' and transmission format 'usmarc'
z3950: 'EGIN' search returned 0 hits
Message processing duration: 30.335

That seems to match the criteria Liam mentioned, time out with an empty result set.