Xerox 242 Problem with Developer or Drum

I´ve changed several times the colordrum but still has the mark i attach in the picture, can it be the developer. I have a blue line in the printing after a few prints and the colordrum gets how you see in the picture.

 

If I'm not mistaken, those little xerox units have the developing station, drum, and charge wire all in the same component. So in theory, changing the drum, also changes the developer and charge wire. Take a peak at your transfer belt and cleaning stations. If your image transfer belt is shot, or a cleaning station is failing (or rubbing against something it shouldn't) it could be in turn, damaging the drum (or contaminating it with residual toner)