I've never had the Vise IT twist or turn in my thumb hole after it's locked into place. And because of the double anchoring system, I've never had one come out. You have the base glued into the thumbhole, but you also have a molly sunk into the bottom of it to lock it into place. My ball driller forgot to put glue on the base on one ball when he was unusually busy before league, and I threw the ball in practice and the thumb STILL stayed in the ball. Impressive. (On the other hand, I lost a Turbo Switchgrip thumb insert once when it was still in the ball going down the lane, but gone by the time it came back through the ball return!)
This is the only interchangeable thumb system that I've found literally no problems with. They obviously spent a lot of time designing and engineering it to be as reliable and simple as possible.