Grafik T Problem

I just did my first Grafik T job; weird problem with two dimmers (RRT-G25LW). As soon as I snap the cover into place they start malfunctioning(not turning on and off and the third light from the bottom starts blinking. I took off the metal shield thinking it is some kind of RF interference, no luck. The only thing that fixes it is if I don't snap the cover fully into place and leave some space between. Lutron told me to return them to the distributor for an exchange; what could be causing the problem? These should be capacitive technology; static on the plastic throws them off?