Xerox 4110 print quality defect

[Printopia]

I have a Xerox 4110 that gives a double dark line perpendicular to the print direction (see attached image):

- replaced the transfer belt
- replaced drum
- replaced belt cleaner
- replaced fuser heat and pressure rollers

The defect does not show up on every page, i does so about every 4-5 A3 pages, which confuses me even more.

As you can see in the attachement, the defect is made up of two darker lines. The width between these lines varies slightly, as well as the position of the lines on the page. When I make a solid print with 20% coverage, the lines are not dark, but merely 'fuzzy'. Very rarely the defect repeats itself on one page, the repeat distance being about 12,2 cm (about 4.8 inches).

The defect shows up in both print- and copy mode.

Although I have the service manual, I have no idea what the problem is. Would be extremely helpful if anyone could help me out!

[Craig]

Charge Corotron maybe??

[Printopia]

Thanks for the tip, but I doubt it since it has been changed along with the drum unit. I got a suggestion to look at the developer trickle port. I'll post here what the outcome of that will be. Meanwhile other suggestions are of course welcome!

[Craig]

What about crap caught between the mag roller and metering blade?

[Printopia]

I'll look into that as well, need to take out the developer anyway, thanks!

[Printopia]

Tried to clean de developer trickle port, but couldn't find much there. I opened developer and used a toner vacuum cleaner to clean excess material and the metering blade, but with no effect at all. I've attached 2 close-up pictures of the defect. Does the developer still look like the problem, or could it be a problem with a drive stalling very briefly, causing a jitter? The problem occurs every 5-8 A3 pages.