Konica Minolta C451 ghosting problem

[kico-abaco]

It is ghosting only black color and ONLY when duplexing (first side is OK, just second side is ghosted).
Black parts of print looks like smeared in direction how paper moves through printer.
Printer is 5 years old and has 200.000 prints, I use Katun toners for past 1,5 years.

Any suggestions?

 

[kico-abaco]

Here is the sample how it looks like.
It smears only 80 & 100 gsm paper duplex side. 170, 200, 250 & 300 prints normally.

http://imageshack.com/a/img31/9041/sqqs.jpg