My x button is not working

Recently, the x button on my controller has stopped working. I plugged the controller into my computer and ran the “Game controller tester” program. It verified that the x button is not being recognized when it is pressed.

I already took the controller apart and cleaned everything and it is still not working. Additionally, I tested the rubber part that gives the input to the motherboard when the button is pressed, and it works for every button except for the x button.

This leads me to believe it is a motherboard problem. Is there a way for me to fix this motherboard or do I need to replace it? Additionally, is there any way to identify if the problem is with the top or bottom motherboard? The bottom motherboard is the one that has the button signal on it, however since both motherboards connect to one another I am not sure if my problem resides in the top or bottom motherboard.

In the picture above, it is the button input that is circled.