(Did a search and couldn't find much of anything on this, surprisingly enough)
The stock buttons on an hrap of mine are a bit loose. By that I mean the entire button literally slides a few millimeters within the panel. I'll be replacing them with seimitsus but I'm not sure if the problem will persist after replacing the buttons. Not all the buttons are loose but about half of them are, some a little worse than others. Anything I can do about this to make them not slide?
Buy buttons that screw in rather than clip in. That's what I used to replace the stock buttons on my HRAP and I've had no problem with them slipping around since. You can get Seimitsus in both types.
Everyone I know who has owned older HRAPs have had the slidey buttons, and snap-in Sanwas and Seimitsus definitely don't do the same thing. They fit a lot more snug.