Pro 951 - back side image position varies

[Takhnamishvili]

Hi all,

I have a strange problem on Bizhub Pro 951. Customer uses A3 80gsm plain paper and after adjusting and matching both sides from "both sides adjustment" menu, it starts printing perfectly, but after 3-4 printouts, back side image starts shifting and skewing. For example: 4th sheet's back side image is shifted by 2mm, 5th sheet's back side image is shifted by 2.5 mm and so on. I tried cleaning registration roller, cleaning rollers in duplex section, stretching springs on registration roller, adjusting registration loop from service mode - nothing changed. I tried to print also on 170gsm paper, same problem appeared. Had anyone the issue like this? any suggestions will be appreciated.

Thanks in advance

[Toxic]

What is total counter?
Does always back side shifts or it happenes on front side also?

[Takhnamishvili]

What is total counter?
Does always back side shifts or it happenes on front side also?

Total counter is approx. 500K and it only happens on the back side