Print jobs that have errored or been cancelled remain in the print supervision queue (PSIMP) (Printouts, Printouts, Print Supervision)
In some cases, if these print jobs build-up, further print jobs may be halted, and printing stopped.
This issue is caused by a defect and a new feature is planned to be introduced in Print Server 2.29.
Jobs will be kept in the queue for 15 minutes.
Restarting the print server clears the queue.