What Mask are you using in File locations for Sync, it determines how files are saved on the device.

Which Build of MMW (Help > About) are you using that experiences a crash on tagging Disc#?

I have found a bug in the program, which is in MMA. I have my MP3 collection synced with my desktop. Here is the sequence of events.
- I add a track to a playlist. I play that track on my desktop, on MMW.
- I sync my collection with MMA on my Samsung S10.
- Let's say the metadata contains a non-empty entry for the Disc # field - let's say it is 1, for simplicity, and the filename on MMA is Disc # Track # Title; in this particular example - see the screenshot - the track title is "101. Electricity"
- After syncing, the file is renamed on MMA (but not on MMW) as "1. Electricity".

As an aside, if I highlight an album where the Disc # field is non-zero, and I make that field empty, click OK, MMW almost always crashes. I have no way of telling if that bug is related to the bug above.

I have screenshots for the above also.