Canon IR 2000 black line (on drum)

I have a black line (1/2'') that keeps coming back ,even if i change the drum unit it will last a couple hundred copies and then it comes back seems like the blade is flipping but it's always at the same place (3 inches inboard) i even change the side door with the transfert roll ,the dev ,so right now i'm out of ideas :confused:,if someone have seen this , your feedback will be more than welcome!!.

Thanks in advance