Did you try a Test (Advanced) for one of these problem servers?

After my updates I did a Test for every single job ... 

Previously I did not run a test, but now I did and I see "Successfully finished connectivity tests in function: TEST_CONNECTIVITY" in the log. I assume this looks promising.

All the domain backup jobs run properly, some of the po backup jobs also run fine, but most of them got stopped a few minutes after the start.

Update:

looks like the gwdr upgrade on the client side happened about the same time when the job stop request has been issued. And for some reason the upgrade happened multiple times. On the 12 and 13 of December. I've restarted the gwdr process manually, will see what happens tonight.

Btw do not forget to upgrade your GroupWise rpms too if necessary.

Update 2:

Looks like the manual restart of the gwdr clients solved the problem, all 80 jobs finished successfully this night.