Clean the wipers with a q-tip and electronic cleaner. Let it dry. Repeat.

Be aware: Do not let fingerprints or residue from the Q-tip get stuck.

I have no idea why they are so different in color. They were paired from top to bottom, but only one of my sticks was acting weirdly.

I tried removing the corrosion (?) soaking it in rubbing alcohol over night, but it looked the same. I guess these wear out pretty quickly, but they are 3$ for 10x on Aliexpress.

PS: After several hits and misses, I used the darker ones on the horizontal axis of the controller. Have no idea if this will help or not.