C450 background 2nd side

[lanierboy]

Hello All.

i have a c450 that prints ok except for double sided black.

when the customer tries double sided black print or copy you get a double image/black background on the second side. colour is fine.

we have changed the black IU and transfer belt plus FW at latest.

any ideas????????????

thank you.

[Si@danwood]

Gen toner?

[lanierboy]

yes toner is from konicaminolta