There's a few bugs that I personally experience, don't know if it is what everyone experiences:
1. Turning Off Arrancar Release disables stat boosts from res (Easily fixable in game).
2. Upon trying to train in GM room for 5 mins after a tourny I usually end up not being able to train at all about half way through. When I get sent back to the hospital I end up still not being able to train, and I have to relog.
3. I don't think Baraggan's res works properly the first time it's received. Most of the time people get it fixed by switching to another res and then back to Baraggan's.
I'll add more as I experience them.