HP M553 Printing light on one side

I have an HP m553 It all of a sudden started to print light on one side.

All Colors are printing but they equally fade on the left side.

sample is here

https://drive.google.com/file/d/1H_ixkHV...

I have 2 of these printers I compared them both in this document.

I have changed all toners! I have replaced the fuser with a new OEM, I have also swapped out the transfer belt from a working m553. Nothing has helped.