Unfortunately the caps of the PS5 DualSense Joypad break after some time of heavy usement. Buying a new joypad is expensive and not necessary, as you can exchange this part if your joypad is technically still ok.
We offer here two thumbsticks in one pack. To exchange it you need a small screwdriver and patience. If you do not have a screwdriver, you can get one on our shop as well.