I have a little light-weight WP Jones rook rifle that does this, leaves stand up with recoil and if not noticed, second shot qoes way high!
I just put a smear of grease onto the flat beneath the leaf and pressed it down. Works for many trips to the range, then very easily replaced.

Sorry, I always seem to be guilty of applying the KISS principle.....

Too bad if you want them to stay up, though....