I am getting exactly the same symptoms on my unraid server. Any time I spin up PMS then 100% of one cpu core is used by plex, with no mention in the logs that I can see of what it is doing.
Did you find any solution to this issue? I have been seeing it for about 2 months now, there are quite a few other people posting about it on this forum but not one of them get a decent reply about what it could be. It always seems to involve PMS installed on Linux in some variation or other.
I have attached my logs in case anybody from support would care to take a look.
A couple of other people I found with the same symptoms and no reply:
