We have an HP color laserjet 3500. Just recently, it started printing funny. There will be horizontal faint lines across the page. Not additional lines printed, but faint lines where there is no color, if that makes sense. Also, it will sporadically stop printing black. If we print out 20 pages, some will be fine, some will have the rest of the colors but no black. We have tried replacing all toners. Would this be a fuser issue? I would hate to spend 300 bucks and have it be something else.