The background has been there for me since it was installed. It’s light enough that customers don’t notice it, but it does change the brightness of coated paper. It becomes more evident when the black drum starts to reach the end of its life but replacing the drums never eliminates the toner background.
I never had this on my 80 and another shop that upgraded from a 180 to 280 said the same thing. They never had the background tint with the 180 but have it with the 280.
If your techs find a solution, please post.
I sure hope toner isn't going to be a problem again. It took almost 2 years before I was running without loosing drums to bad batches of toner.