SC couldnt get backup progress from DFM which could be communications issue or something with DFM.
I recommend setting RUN_PM_BACKUP=N to avoid this until it is figured out why this is happening.
I have never seen this issue personally so my guess is communications related. What version of SC and also what other messages do you see? There should be some ZAPI messages? Zou can look and see what API SC sent to PM and see what came back, this is in debug output.
We have had the same Issue after upgrade SC from 3.5 to 3.6 (Oncommand 184.108.40.20636). We don't find a solution, so we have to go to 3.5 again. Since the downgrade
it works without any Issue (few Months). Something has changed between 3.5 and 3.6. In near future (When I have a timeslot) i will open a Case about that. When I find a solution with support, i will inform you too...