shared library between old iTunes and music.app

Hi all!

I'm having troubles with my music/media-setup:

I have everything on 2 mirrored hard discs, because it's mostly ALAC.

• There's a mac at home (my good old MacBook Pro 17), which runs iTunes, and is the master (containing the musiclibrary and all files on its external harddisc)
• And there's my Mac Mini (late 14), running 10.15.1, and consequently the newer "Music" app'. This device has its own hard disc, containing the mirrored music-library and the files.

Since I upgraded, there's problems:

1. music.app doesn't find new files. They're displayed as "in the Cloud" (although the library should direct them to the physical file on the local HD. But this is only for some files, not at all all of them! This happens even if I delete the new musiclibrary and start Music from the "master-music-library.lib" on the hd.
2. music.app can't update the library from the cloud. It connects (through a hot-spot) and hangs there. sometimes it tells me that "something/some error occurred.

I understand that there may be some compatibility issues, but that stuff is strange. And—is there anybody having those issues too? Could they be solved?

Thanks!

david