On starting signer with faulty conf.xml to trigger error ods-control signer start hung and I noticed this in the log:
Apr 24 13:19:32 centod64-ods03 ods-signerd: [engine] signer shutdown
Apr 24 13:19:32 centod64-ods03 ods-signerd: ../../../signer/src/daemon/xfrhandler.c at 178 could not pthread_kill(xfrhandler->thread_id, 1): No such process
This does not happen every time.