I have the same problem. I copied the files to my Lenovo tablet just by treating it as an external device and using windows drag and drops to copy my music folders (over 7000 MP3 files).

About 98% have been logged in the MMA database ok and browsing by track, album and artist is fine.

A hundred or so have ended up with Unknown Artist, the Album name is empty and the track title has been inherited from the folder name and file name, even though the tags in the original files in MMW are all fine. Is there a reason for this?

I will however clear the files from the device, and try the sync process you've described above.

How did you copy the media files to the phone? Did you Sync with MMW (recommended)?

Have MM on my laptop runs fine. Installed the MM app for my android phone and it shows all artist in my library as unknown. I do I get the app to list the track artist?