I installed my cab lights about a month ago (5 piece 88-98 chevy). I had one leak about two weeks ago. So, I take the lenses off, run a bead of clear silicone under the base of the lens, remount them, then place a dab of silicone around the screw holes. I tightened them just enough to seat rubber base then quit. Ok, I inspect them last night and ALL 5 OF THEM HAVE SHATTERED! Front to back from the screw holes. What happened!? I know that I did not overtighten them. So what gives? The silicone? Funny thing, new lenses cost as much as a whole new kit.

Suggestions?