Hopefully Tracy is on the right track. However, from your post, it sounds like the machine has been in place and operational for a time, as opposed to being installed, which means you might actually have a laser dying.
You need a technician to work on the print head.
I run a Screen 8600 and Screen 8000. The 8000 was famous for bad diodes. We upgraded the building ground and it stopped losing laser diodes. When a laser reaches the end of its life, it will no longer be able to generate enough power to image the plate, no matter how much power is being sent to it.
And it does take a technician to work on the print head, laser and optics. There are some landfill parts in there... meaning if you bump them wrong, the whole machine is landfill. Do not go blindly into the printhead.