Some buttons on Dualsense not working

I'm trying to fix my brother's dualsense controller; He got it used from a rental store, so I don't know what may have happened to it before that that may have caused this. When my brother first asked me to take a look at it, all the buttons worked except for the d-pad, which didn't work at all. I took it apart and cleaned the buttons, etc., they weren't that dirty. I didn't see any signs of damage that I could recognize. Now I've put it back together, and you can navigate the PS5 menu with the D-pad but it always moves to the left, as if the left D-pad button is always pressed (which it's not). And now some of the face buttons, namely the X and Square buttons aren't working, even though they were working before. Any help to get the controller working would be greatly appreciated; I'm very much an amateur, and I assume I'm probably making a basic mistake.