I came across this post in a Google search, we were having the same errors in the policyagent.log. Our problem turned out to be caused by some bloated Kerberos tokens and we had to modify some registry keys on our Management Points to resolve. I posted a blog with the full solution that worked for us, maybe it will work for you as well.
http://blog.configmatt.com/2018/03/resolving-issues-with-user-policy.html
Figured I would make an account to post the solution for the next person that finds this via Google.
