The buttons are simply tabs that press down the hard button on the phone.
Since they are just on the case you can adjust them a bit.
DO THIS AT YOUR OWN RISK.......... Everything below is about modding the rear cover, not the phone itself. Do not mess with the buttons on your phone.
If they feel a bit too flat you can mix a tiny bit of epoxy and dab it on the stem that makes contact with the button. We are talking an amount the size of the ball in a ballpoint pen. Apply it flat (don't let it dry rounded, flatten it out) and then try it again after letting it dry (2-part epoxy dries in a few minutes). If it is too much you can take a razor and trim it down.
On the flip side, if the button sticks up too far and is too sensitive you can shave the post down with a razor.
BE CAREFUL, one slip will mess up the cover. Just putting this out there so people may have an alternative to try before ordering a new cover.