I have a solution to this problem. I converted the Battle-Meteor Admin.mp3 file to .OGG, renamed it back to Battle-Meteor Admin.mp3, and replaced the old one.
Now the music in the Meteor Admin battles loops just fine without freezing . . .
I'm really not sure why this issue occurs since the other .MP3s work fine . . .
A (sendspace) link to the converted file:
https://www.sendspace.com/file/k2dt72
I have also fixed the .MID files in Pokemon Reborn\Audio\ME by converting them to .MP3, renaming them back to .mid, and replacing the old ones.
I can upload those converted files too if anyone would like them . . .
I think the issue here is ultimately due to Wine expecting OS X's built-in audio framework to play MIDI files, but native MIDI support was removed several years ago . . .
I have also noticed this, but I don't have a fix . . . It seems to be related to how Wine handles Sleep/Idle under OS X . . .