I've recently found that when the 'preserve folders and filenames' device sync option is selected only 2 parent folders of the file are preserved.
It used to work fine, and looking back at some other sync/backup logs I have it appears to have changed earlier this December, maybe around the 9th/10th. I didn't apply any updates to MusicBee around that time and was still using 3.0.6262, so I have tried it on a fresh install of 3.1 update 1, on 2 separate computers, and the problem is still there.
So for example, if the full path to the file is D:\Music\Albert Collins\Album 1\musicfile.mp3 then the synced file will be E:\Sync\Music\Albert Collins\Album 1\musicfile.mp3 which is correct.
But if the file is D:\Music\Albert Collins\Album 2\Disc 1\music file.mp3 then the synced file will be E:\Sync\Music\Album 2\Disc 1\musicfile.mp3 which is incorrect.
So it looks like its only preserving the immediate 2 parent folders of the music file. It's the same thing no matter how deep the folders are.
Can anyone else reproduce this? There's nothing in the error logs.