After reading your OP, I tried playing my Beatles playlist with Roon ARC over cellular. It includes 216 Qobuz tracks and is playing well. I think most of the tracks are only 16/44.1 if that makes a difference??
You could try deleting the Roon ARC app and reinstall.
Well, whole library, not downloaded. I saw on here if you want to shuffle whole library or songs in Arc you need to make a playlist. Smaller playlists do work tho.