I am using beaTunes to analyze my music collection and add tags, mood and color to the files.
After beaTunes saves the changes mp3tag cannot load the MP4 tag info anymore.
This is only repro for m4a files. I confirm that Windows Media Player, Windows Explorer, or TagRename can read the tags successfully.
See attached screenshot for more details:
If you need any demo files to repro and investigate please send me a message.