Post mortem:
Over the past few days, the SQLite DB Sonarr uses was partially degrading for reasons we're not sure yet. Restoring should of been easy, and is a documented task with step-by-step instructions.
However, we discovered that the automated backups of Sonarr had been corrupted due to our script copying the ZIP file produced by Sonarr whilst it was still making the backup. Our script simply waited 5 seconds after sending the backup request to *arr.
We didn't detect this initially wh...