What sensors in the Meta Quest 2 controllers control hand tracking?

I am in the process of repairing meta quest 2 controllers at the moment, and I keep running into an issue where I replace the joystick on the controller, but then I go to test it afterwards and my thumb just hovers on the joystick and will not move unless I actuate another button. My thumb just jumps back to the stick after a different button press. It doesnt track my thumb hovering on the A or B buttons either, only when I actually press the buttons is when my thumb will stop hovering on the joystick.

What sensors inside of these controllers control the "hand tracking" while using the controller? I have ran into this issue with the rear trigger as well.