Ok so the problem with the Joycon's Joystick got fixed (somehow). But there's still one problem: the SR button in one of my Joycons isn't working. So it's impossible to connect it if I wanna play with it sideways in games like Super Mario Party and Mario Kart 8 Deluxe. I tried disconnecting it, but the disconnect button ALSO doesn't work. What do I do?

Dr. Mario

Mushroom Kingdom's OG Woo Meister
Or you can try to disassemble the joy cons to see if there are foreign materials jammed in there. I'm not sure if they sell buttons separate, but I know you can manually replace the control sticks for the Gamepad for much much cheaper (compared to buying a new Gamepad) so I assume you can do the same for joycons.