Scroll wheel not working, presumably due to dropping hard on the floor

The scroll wheel doesn’t respond. There are some rare occasions when the scrolling responds again, albeit poorly (scroll direction is always down regardless of wheel spin direction). So I’m thinking something might be dislodged around the wheel part of the PCB. I was trying to measure any voltage on the base of the wheel sensor or whatever that is, while trying to spin the wheel. But I’m just not sure if I was probing on GND or any useful pads on the PCB. Is there a schematic diagram + PCB layout of M331 somewhere? In any case, I feel like there is just a disconnection somewhere that has to be resoldered or reconnected.