Does your controller wander without you touching the thumbsticks?
 
This is what is called stick drift, where one or both of the thumbsticks thinks it has input and will move on its own accord.

I will carefully open your controller, clean and inspect for damage, fix the drifting stick by way of soldering in a device, the controller is then tested and documented, packed up and returned back to you.

I aim to have your controller back in your hands within 4 days of me recieving it.