+1 to this, same occurrence when using same agent along with downgrade fixing issue.
While on 1.41.7.9717 Attempted fix of renaming the agent in info.plist and renaming agent folder to match in a an attempt a reset, same error is presented.
Error in logs:
metadataagentpostprocessor: failed to find agent for identifier com.plexapp.agents.shokorelay
Edit:
Attempted plex dance as well on 1.41.7.9717 (prior to Info.plist change and after), just ended up with whole library that had no metadata due to error.