After going back and forth between my media player, MusicBee, and Mp3tag trying to duplicate this issue. I figured out that MusicBee is causing an issue when for some reason it splits the fields when I never told it to. It looks to be some kind of bug with MusicBee.
EDIT: it looks like there is a bug in Mp3tagger. It is not showing the \\ as a field separator in the custom field I made %VOCALS%. However, it does show that there are two separate fields for Vocals.