Command Button Size Increase / Decrease

I'm building a keypad out of commandbutton controls, and there's this strange resizing behavior with the commandbuttons. I've attached an example, as it's much easier to see than describe.... but essentially, clicking a button seems to enlargen it slightly, and then two clicks later, it 'dezooms' back to original size (even with shadows turned off). while this is not hugely noticeable individually, it feels really strange when there's a whole keypad of commandbuttons.