Running a big collection update on my end, I found this issue the last couple of days. I saw the chat about a rate limit being implemented in TPDb and also a new commit for PMM that should work around this somehow.
This commit has been in effect for a while but I still did not see any changes in Plex, so I took a look and ran the command twice; the errors start at the exact same poster each run. I have created a test config to limit the time it needs to complete so we can specifically test with that.