I received a call back regarding my case. The following is what I was told.
This is a known issue with both 6235 and 7170.
1a. If using 7170 and experiencing the missed job problem, apply hot fix 13, then go to step 2.
1b. If using 6235 and experiencing the missed job problem, apply Service Pack 1, then go to step 2.
2. Wait and see if your backups still get missed. If everything is ok, you are done. If you still get missed, go to step 3.
3. Place all existing jobs on hold. Create all new jobs. Do not use any existing selection lists or policies in the new jobs. The new jobs must be completely new. Make new selection lists and policies. Schedule the new jobs. Symantec says that as long as you did step 1a. or 1b., then this will definitely, for sure, fix the problem. :)
I have plenty of servers of each revision and will post results soon.