Just a stab at this as my library did something similar.
- set sonic analysis to run as a scheduled task (likely already done)
- optimize your library (this will flush cache, remove old bundles, etc. usually once a week)
- restart plex application to flush ram.
it should start after a while. it says relatively nothing about what particular album it’s working on (unless you enable debug logs) but there’s no way to manually trigger it aside from changing the scheduled task maintenance window.
good luck
