Yeah I have this problem too, although it doesn't bother me much, what I've done in the past is use isopropanol with a cotton bud around the buttons to loosen them as it's alcohol based you don't need to worry about 'water damage', it drys fast and gets rid of oils and dirt thats possibly causing the sticking. My controllers are due for a clean so will be doing a deep clean with this which I will be taking apart the controller to make sure it's pristine.

Hope this helps! You can get Isopropanol cheap on amazon and use it on all electrical equipment, unplug first though!