Started getting complaints on slow delivery of emails and looking at headers it appears that emails are getting trapped in the service for a few hours (2-3 hrs) before coming back out. In logs I see this happening about every minute or so:

Aug 30 16:28:02 2024 (2301) send_digests() failed: maximum recursion depth exceeded

I have restarted most services and after that failed to resolve the issue rebooted the whole server but the error persists. We don't use digests and there has been no changes to the system in some time. Also this is the first time this has occurred. Any clues on how to resolve and possible prevent this from coming back?

Also starting to see this in logs:

"Failed to unlink/preserve backup file:"