Hi,
From your attached images it looks like magenta drum is very used. Replace the drum.
I Have a Workcentre 7775 that has some print quality issues and I'd appreciate any advice going on what the cause is likely to be. Attached is a copy of the Drum Test. I switched the Cyan with Yellow drum and the lines are yellow after printing. I also see the lines pattern on the transfer belt. I would appreciate some help on this issue.