I'm not sure I fully understand the problem; however, I will share my experience with my rear tail lights. I replaced the OEM lights with a set of smoked ones. The right rear tail light wouldn't work and what I found was that when I opened up the light and looked at the piece that houses all of the light bulbs, one of the light bulbs was not seated firmly. I re-seated it and it worked for a little while. When it happened again I noticed the bulb came unseated again and found the metal "strappy thingy" to have flexed out of its normal position whithin the black plastic piece. I re-seated the metal "strappy thingy" and haven't had any problems since.
Bottom line because I don't think I'm being very clear, check to make sure the light bulb is properly seated and check that your metal "strappy thingy" is not coming apart from the black plastic piece.