Plex is not respecting the configured maintenance window for scheduled tasks. My window is set from 8:00 am to 11:00 am. The fans are spinning quite loudly. The dashboard indicates thumbnail generation still processing at 11:25 am.
I believe this glitch is caused by a lack of granularity in analysis processes. Plex should be able to pause and resume its analysis process at a much deeper level than per-show or per-season or per-movie, down to individual frames of individual videos. That way, analysis can properly pause immediately when the end of the maintenance window is reached.