Do you have a button that doesnt always register when you tap it? 
Are you having to repeatedly tap a button, to only miss what you were tapping for, highly frustrating, I know.

This can be caused by a number of things, so a full strip down and clean, rebuild and test, untill im happy its 100% working.

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.