prints gray lines and black spots

You have a grounding issue in the printer somewhere :-(. That said first thing I would check myself on the off chance the printer is fine is your household ground - while it's unlikely to do this fault, some printers might tie into the household ground so deeply it's not out of the question. Any outlet tester from a hardware store like Lowes will do the job; doesn't need to be be fancy.

If the household ground is good, you want to locate the ground strap location in the printer. Typically, it's by the corona wire or PCR, but yours uses a corona wire. Once you find the corona wire ground point, take the printer apart from the side where it is located and see how it is done. For example when I ran into this on a DOA Lexmark, the ground point was on the power supply and if you got it wrong (or miswired it) the printer would do this behavior until you hooked it up to the right connectors on the PCB. Then you had to make sure the PCR ground was connected. That fixed it when the image was bad and the seller did not want it back, and let me keep it, so I messed with it and kept it for the components like the fuser being at 99-100% health. It had other issues like a major gearbox fault, which were hard to track, so I condemned the printer due to the complexity of the fault, but I kept it for the remaining parts.