Dimmers work fine until I snap the plastic cover with the metal shield on. Some of the dimmers then would not dim all the way down; they would flicker at the 3rd LED light from the bottom requiring power off from the pull out tab. If I take off the cover they work fine again. First thought was the metal shield is causing some kind of interference so I took it off. Didn't make any difference; I then replaced the bad dimmers as per Lutron. Two of the replacements are now acting up again. WTF? Any of you guys seen this before?