I have swapped out the drum, fuser, side transfer unit assembly but still the same line.

And it's only on the first page.

Thin line is about 1 1/2 inches from right side and is all the way down the page.

Comes back if the machine sits idle for a minute.

Board issue?

Hoping someone has seen this, machine is slightly old. (Yes, I know, about 12 years or more?)