Board Thread:General Discussion/@comment-25642086-20141129034641/@comment-8986886-20141129105228

I don't presume to be an expert on the workings of the Bleach universe, but I do have some theories that might satisfy your curiosity. I don't really have a good theory on Quilge and Ayon, though, so I'll leave that for someone else to explain.

Q : "how do the bankai return to the shinigami?"

A : Either the medalions are unable to seal Hollow Reiatsu, or the Sternritter chose to release the Bankai so that they could activate their Vollständig, which were inaccessible to them as long as they held on to their stolen Bankai.

Q : "why would the medallions seal break to release the Bankai simply because it hollowfied?"

A : The Sternritter had to have come in direct contact with the Bankai, in one way or another, otherwise they wouldn not have been able to control them in battle. That contact, be it psysical or spiritual, would have tainted both the Sternritter using the Bankai, as well as the medalion holding it.

Q : "when the quincys lose the Bankai why not simply wait for the hollowfication to wear off and steal it again?"

A : Even if the Sternritter had known that it was a temporary Hollofication, they would also have expected the Shinighami to simply do the same thing the next time their Bankai were stolen. Like I mentioned earlier, the Sternritter were also pretty eager to use their own Vollständig.