Thank you both for the descriptive responses @Norman_Spector and @Placebophile.
It’s no problem to play music via Roon during the sync - I recommend trying to allow the sync to complete.
We’re also testing some new download features over in Early Access (there was an EA ARC release yesterday. It might be worth switching over since you’ve lost a large volume of downloaded content.
In the meantime, we’re investigating these reports and will activate diagnostics for RoonServer. We should know more soon. Thank you for your patience.