Bizhub C250 intermittent dark images

[mattwill1107]

We have a Bizhub C250 that is intermittently producing dark gray background, but image is still visible, both on copying and printing, color and black and white.We have updated the firmware, replaced the black pcu, and the high voltage unit. Problem seems to go away for up to weeks at a time, then returns. Any thoughts?

[copytechman]

Drum ground not always contacting the frame very well, I had a c250 do this too and you can recreate the symtom by running copies and rocking front of any IU up and down to make and break the drum gnd.. I had to um reform the drum ground contact to make it contact the frame more "aggressively", havent had a callback yet.
Regards.
A.