I have an FS-C5030DN with image problems. After a few prints, the toner builds up on the black developer unit/ mag roller area and starts dropping onto copies. Also, the lead edge on the back of the print has about a 2-3" background. ALSO, the entire page has a faint background of gray lines a few mm apart. I have tried both HV bias boards, the black developer unit and I swapped the black drum with the yellow to see if the problem followed. It did not. Anyone seen this?

you need to check to developer bias board check the conector for the black developer i had one that had a cold joint for the ribon conector