Printer issue

Looks like a cheap refilled cartridge issue? The transfer roller is dirty (you can't really clean it) and that area is holding toner from one pass to the next.

Edit> The give away as to what the problem is should be the size of the roller. If you can roughly work out the circumference of the rollers then you can see on which one its the same as the repeat.

If you dare you can also switch the printer off mid cycle before the paper has gone through the fusion roller and then you can see if the problem has developed before the fusion roller. Doing this is a bit messy as there will be a bit of unfused toner on the paper.

I probably shouldn't comment as you were trying to be helpful but that is never going to fix print contamination due to a damaged component. The evidence is in the picture in the OP.

I have the B/W version of that printer and the pattern repeat looks to me suspiciously like damage to the fusion roller which is part of the toner cartridge. So my first guess is the OP is using a cheap refilled B/W toner cartridge? I have seen similar on many occasions on other printers. I've also seen worn out fusion rollers but thats very rare.

The thing I forget to suggest earlier was removing the B/W cartridge and carefully without touching it examine the transfer roller. My bet it that you will see the same pattern on it as is coming out in the print job.

I don't suppose you are in Cork ? or could recommend some one to sort out my Epson L355 ,

I cleaned the heads ,all went well UNTIL Idropped a screw into the printer , can't get at it without disassembly or just chancing that the screw will stay out of the way ,

New eco printer would cost around 250 so repair /screw retrieve would cost who knows what , any suggestions appreciated