There was a thread stated several months ago with the same or very similar issue. It was found that the button on the board inside the mod had come unsoldered causing the outer button to not have anything to really push against, thereby collapsing.
You'll need a new device. I'm all for fixing things but this isn't worth fixing 'cuz if you get it disassembled it may be impossible to reassemble it anyway. This is a semi-disposable device.