Hey Conor,
First thing your Build version. It is very old and a lot of bugs have been fixed now.
Current available build is M33.104. Please do upgrade.
Have you searched SAP notes for your version? If it is a bug it would have been mentioned in the note for the next build version.
What do you mean the job suddenly stops? What do you see in the job status?
Is it a recurring job? Have you checked the schedule calendar of the particular job in status area?
Also make sure, the time window on which is the job is running is closed for that time.
Also check the submit frame. Submit frame is closed if the corresponding time window is closed.
Thanks
Nanda