I've been debugging this solo, but came across this thread and wanted to share my experiences in case they might offer some pointers. Unraid has been bulletproof for me until now – I'd love to help you guys with this if I can!
I've been having regular corruption over the past week or two. It first occurred on 6.7.0, and has definitely become worse on 6.7.2.
A couple of days back I created two new shares – Plex AppData and Sonarr AppData, configured both to prefer the Cache (but exist on disk1 only), pointed both Plex and Sonarr there via /mnt/user/[app-specific share]/ and that seems to have potentially fixed the issue – the corruption was nightly before. I'll keep watching.
The sqlite3 .dump and re-ingest trick has never worked for me when the databases have corrupted.
I also noticed that when Sonarr's db hosed itself, Plex's performance for the TV library became abysmally slow – often timing out. Music and Movies were unaffected, and still loaded. As soon as I stopped the Sonarr container, Plex performance recovered.
I've attached my diagnostics in case it's useful.
tower-diagnostics-20190801-1307.zip