I'm running openmediavault-plexmediaserver 3.8.2 and PMS is pegging at 100% CPU. Tried all the standard Plex troubleshooting steps such as disabling automatic scan, music library volume detection, etc... Very frustrating, and couldn't find anything pertinent in OMV forums. I did find this recent bug involving SSDP and UPnP:
https://forums.plex.tv/t/100-cpu-usage/358226/15
Hoping they fix it soon and that the OMV Plex plugin gets an update shortly after