DP 5.5: faulty job queueing

[FDomnick]

I'm using DP 5.5 with the cell server running on an HP-UX 11.
There are 4 jobs running overnight with these sheduled starting times:
#1 11:30 p.m.
#2 04:00 a.m.
#3 05:00 a.m.
#4 05:30 a.m.

Every now and then job #1 is taking longer than expected and is delaying job #2 to end after 5:30 a.m. In such cases DP does not continue with job #3 - although I already have increased the value for SmWaitForDevice to let the jobs wait 90 minutes to start - but leaves it waiting in the job queue and starts job #4.
Thus job #3 times out and is lost for that day.

What can I do to force DP to run the jobs as queued?

Kind regards,
Frank Domnick