Went to it and opened the controller myself to fix the "sticky button" syndrome (I live far away from easy RMA's). The only tricky part was removing the top cover that has been glued. Used hair dryer to soften the glue and then carefully peeled it off. The rest are just screws, no need to touch the "led ring" or those screws at all. When assembling it back together, you will have to remove the battery compartment to re-attach at cord on the back of the "button" electronics board. The amount of glue on the top plate lends itself to just re-attach it back in position when done.
The problem seems to be a small (3 times 5 millimeter-ish) rubber pad behind the trigger button that has been glued to a flat area, but then becomes unstuck and wedges itself a little off, or somewhere else.
More details please, I have the same issue and don't want to send for replacement. Did you have to remove the top panel (where the buttons and thumb rest is) or could you get straight to the trigger?