I literally just had this exact thing happen to me, it started as a baboon, then went to cranberry or something, then mongoose... I had to completely reset my Xbox to even get back to being able to play online, and come back to an Oathbreaker, with my clanmate and the blueberry we were playing with..
The Oath Breaker problem is a joke. Some how I was booted out of the match and now I receive an Oath Breaker wait for something I didn't purposely do. A complete joke! Apparently Bungie can't detect the difference between purposely leaving a group and an error I can't control. The best part is Bungie makes you feel like you did something wrong.