How to identify which connection is causing error 17886?
You can do this with an Extended Event Session.  EG
CREATE EVENT SESSION [TrackError_17886] ON SERVER 
ADD EVENT sqlserver.error_reported(
    ACTION(sqlserver.client_app_name,sqlserver.client_connection_id,sqlserver.client_hostname,sqlserver.client_pid,sqlserver.session_id,sqlserver.session_nt_username,sqlserver.username)
    WHERE ([error_number]=(17886)))
ADD TARGET package0.event_file(SET filename=N'TrackError_17886')
WITH (MAX_MEMORY=4096 KB,EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,MAX_DISPATCH_LATENCY=30 SECONDS,MAX_EVENT_SIZE=0 KB,MEMORY_PARTITION_MODE=NONE,TRACK_CAUSALITY=OFF,STARTUP_STATE=ON)
go

Will record the errors in files in your &quot;log&quot; folder.