Same happened for me.
The initial case was closed and told it it is a Hyper-v issue and they need to open the case with a different team.
I cannot believe how your story is same as mine.
Symantec? Are you serious with your product and your support?
WE NEED TO UNINSTALL everything and go back to SP3. I havecase opened and the support do everything to do not escalate to advanced. This is crazy on things take long time to be fix.
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I have the exact same problem. Before SP4 everything was working before and the jobs queued and stuck... The engine seems to have been broken by SP4. Restarting all services is the only way to kick new jobs and may fail again by freeezing,.