My dome light in back seat flickers or you could call it fading in and out when the door is open or turning on the interior light. The overhead light is just fine, I dont have a clue, it's been doing this for a good while.

try getting yourself some diolectric grease and put on it. see what that does.

sounds like some cleaning of the fixture would help. My under hood light was doing the same thing and i cleaned it up and it helped alot, but i believe it needs more cleaning, I have to thump it every so often.

I would clean the terminals and try a new bulb.