I deinstalled MMA and wiped all files in MM directories, then reinstalled.
this solved the problem.
seems that this was triggered by the android update, that added a second path to an existing folder.

thx for all comments.

I had duplicate tracks after a similar upgrade. I just wiped the whole configuration and started over. Remember to check the Device in MMW's options, you probably have a duplicate entry for the tablet.

I can't reproduce on a Galaxy Note with Android 4.1.2. Maybe it's a upgrade problem and you should try removing the files from the device and syncing them again?

my tablet recently received an ota update from android 4.0.4 to 4.1.1
since then tracks show up twice.
the track properties of a track pair show the following paths:

/mnt/sdcard2/Music/Folders/...
/storage/sdcard1/Music/Folders/...

it seems that with android 4.1.1 the external sdcard (sdcard2) is also mapped under /storage/scard1 and MMA 1.0.4.115 does not recognise that it is the same location.

bug?