The left thumbstick clicker button will not click...

Hi guys. My son's Xbox One Afterglow controller's left thumbstick button will not click when the thumbstick is pushed forward. This is super annoying when trying to play Battlefield 1, because that happens to be the run button.

Couple of things :

I dunno how the damage was done, my son did it and he's pleading the fifth...

The button does click on almost all other positions and there seems to be no catchiness in the movement of the thumbstick.

I have noticed the left thumbstick will pull up almost half a centimeter, whereas the right has zero upward play.

Any suggestions or answers you already know are very much appreciated. There had been an aborted attempt to open up the controller but I was weary on how much force should be required to separate the two halves of the case. But I plan on a reattempt...