check your ground that goes to your fender i had to move mine cuz it also did the same thing every once in a while its just the wire thats bolted by the battery area right on the fender with a 10mm bolt
try that and that should solve ur other problem
and ya they put that tab on the wrong side i was pissed when trying to install mine thought they sent me a dead kit lol
edit i just seen u said ur pass side is good, hmmm check and see if there is a ground on the drivers side also though and make sure u flipped the drivers side plug also
but ya my pass side would flicker and it ended up being that ground on the fender, you might want to check that anyway or just follow the wires and see if theres a ground connected on the drivers side also, most likely there will be one somewhere over there