Hi! I don't know if this is solved or not, but I've been having trouble with my metadata from m4a tracks. Whenever I load my .flac albums onto a playlist (just drag and drop a folder of files) they're arranged correctly by track number and disc number. When I try to do the same with my m4a files, they're arranged alphabetically. For the m4a files, in windows explorer I see the correct track number, and everything works correctly and loads according to track number in iTunes. The only thing I've noticed is that I look at the metadata for the files in wacup it shows 1/15 2/15 instead of integers 1, 2... If I manually edit the data, it still doesn't fix the issue.
I used mp3tag to delete the totaltracks metadata from the album, and this made wacup metadata read integers (1, 2...) rather than the fractions (1/15, 2/15, ...) but the files are still loading alphabetically. Really frustrating because all my flac albums work perfectly, and I think the metadata is fine (in some regard) because iTunes is reading it properly.
Hope someone can help!