HP 8550gn

[ATSBMCO]

I have been stumped by the fault of this printer,

It prints with a feint leading edge of about an inch and then the page is fine.
Even duplex has the same problem. The transfer brackets are ok and it has a good solid image on the transfer, the fault is when the image is transfered to the paper.

The transfer unit is new.

[Wild Bill]

This is what I found for the void area adjustments. I also remember a problem with the registration assembly. I would call Parts Now and they will have a record of the entire solution. There were 2 parts to replace.Maybe you can do a cold reset and get it back to factory. Print a config page and remove the jetdirect card
Cold reset
To perform a cold reset on the print engine portion of the HP Color
LaserJet 8550MFP, see the HP Color LaserJet 8500/8550 Printer
Family Service Manual.
Cold reset on the copy module is useful in three circumstances:
after replacement of the firmware dual inline memory modules
(DIMM)
after replacement of the reader controller printed circuit board
(PCB)
if a system settings password has been set and forgotten

[dberisford]

This is surely it!

You may have a cleaning roller issue with a spring on the right side if you open the right side and remove the big drum unit. On the right is a little white clip which has a spring attached. The white clip is made of plastic and the holder on one end for the spring sometimes breaks. HP has a kit for the repair called the ICL Arm Kit. RG9-1527-020C
I replace this all the time!