It's probably all the talk about lasers and water pressure destruction if you want my opinion.

[ He looks a little put out about what's said next, if the pout that's on his face means anything. It's not WRONG, but Vash has been hesitant to let anyone other than Brad anywhere near his prosthetic. When you've had the same guy working on it for over a hundred years change is hard. ]

When you put it that way I can't really argue, haha.