If your buttons do not react as expected when pressing them, you might try cleaning the conductive parts of the silicone pads with alcool. If that doesn't work, you might change them for brand new replacement pads.
Here's what you get:
- 1x D-Pad conductive silicone pad replacement
- 1x Start/Select conductive silicone pad replacement
- 1x A/B conductive silicone pad replacement
These parts are also compatible with Super Famicom controllers.
Keep in mind these are brand new third-party alternative, they might not feel 100% like the originals.