What can cause this problem? Please see the black line. If I make 10 separate prints, the page is 10 times the same, so: including the line with the same thickness. When I make 10 prints at once the line gets more invisable per page. Please see the difference between page 1 and 10.
I already replaced the black drum with a new one: problem still persists. I also noticed the problem still persists when taking out all coloured drums (printer still works) and only having the new black drum inserted. Same problem.
Anyone any idea what needs to be replaced?