C-stick cutting in and out in game?

[JackSSB]

For some reason my C-stick on my controller just stops working in all directions during a match, with no pattern at all. It's only while in game though, as it works perfectly fine in the menus. This also happens in Project M for me. I'm using a 1st party indigo GC controller on a rather old Wii (around 8 years old now). All advice on why this is happening or how to fix it is appreciated!

Edit: I'm not sure how old my controller is, I bought it on eBay about 5 months ago and it's in pretty good condition, but it was definitely used before I bought it.

 

[-ACE-]

Stick box for the c-stick is bad most likely. I'd get a new controller but keep your current one, it'll just take a while to find a 1st party replacement stick box. You might be able to find someone with a junk controller that has a good c stick.