Hi Carol - that exception is the value given to any queue item the process has locked when the process finishes (completed/terminated/stopped). Basically the process ends and it is still 'holding' a queue item, it does not know what to do with the item, so applies a default exception reason.
Usually it is the design of the exception handling in the process that causes this. Check to see how/where your process could fail while it is holding a queue item.