Weird Scheduler issue - non-Robot job triggers inititate 2 x Robot job submissions!

Folks, after several years of very stable operation for the past month or
so we've had a weird situation whereby some Robot-scheduled jobs fire
off twice after being triggered by the successful completion of a non-Robot
job. Robot jobs that are triggered by other Robot jobs continue to fire off
only once.

I've checked the RBTDEP file in ROBOTLIB, and there are no duplicate records.
Previous to this the trigger situation was quite normal - 1 non-Robot job
successful completion would trigger off 1 x submission of a Robot job. Any ideas?
I can't think of any system variables changing (no Cum/PTF; no Robot upgrades,
nothing to speak of . . . ). All help and input appreciated ;-)

Thank you!
Greg Chijoff
Sydney, Australia