Apple Music library & playlists keeps disappearing after Tahoe update

Hi, I've just bought a mac mini M4 and after updating to Tahoe 26.1 now every time I restart my entire library and playlists disappear [around 20K tracks] - even though nothing has changed and the media location is correct.

I've tried 3 or 4 times now rebuilding the library, even tried creating a new one and manually re-created all the playlists looking at how it was set up on my macbook pro and every single time it all doisappears after the mac mini is turned back on - this is definitely something to do with the Tahoe update - anyone have any workarounds?

Thanks