Animeleague

Above.

I tried to sell an old controller at CEX this afternoon, they tested it and said the left stick has a bit of stick drift so they wouldn't take it.

I realise I could chuck it on eBay, mention the problem and lower the price a bit so someone can maybe fix it, but can anyone help me fix it to get a bit more money for it?

I am aware of Google.

 

This has happened on my switch joysticks and to some extent on my pro controller. I've read somewhere that it can do that if is all dusty underneath or something but I would probably fact check it since I sort of heard about that through the grapevine.

Well you don't really "fix" stick drift. You fix the controller. Controllers are consumable items. The stick module is just 2 potentiometers combined into a block, but there are plastic bits inside which get worn down over time and the sticks start giving faulty feedback. The way you fix it is just replace the faulty stick module. You can sometimes buy the stick modules in bulk for cheap. Its worth it to fix it if you're going to keep the controller, not really worth it if you're selling it.
And yeah they can just be dirty, but there isn't really a way to clean them. You can try to lubricate them with some light oil and hope it cleans up.