Vertical line on printed copy

change copy setting from normal to best as a work around

clean the drum of the toner with tissue paper and reinstall hopefully it will resolve the issue

Usually replacing the toner cartridge fixes that problem. Sometimes it's the fuser.

If the lines are vertical to the direction of the printhead movement, you need to clean the paper rollers and the small "pizza wheels" of your printer. Also check for any traces of stuck paper in the paper path. I recon you ars not using genuine inks, right? Try to slow down your print speed by selecting a best quality setting.
If the lines are parallel to the printhead movement, your printhead is either clogged our stuck.

Check your flat bed and Document feeder scanning glass need to be clean, if any dot or dust in scanning glass of document feeder it will appear a line, check this points first
1- Check printouts from computer or FAX if it is clean problem in scanning section
2- Check using Copying a blank paper using only Flatbed if it prints without any line its problem from document feeder Scanning glass
So solution is clean the Document feeder scanning glass using wet cloth, note careful about wet cloth switch off the machine and clean it

Remove cartridge observe on cartridge drum finds any vertical toner line? replace cartridge, as well as check all cartridges same manner...if found replace them..If its only on copying: clean flat bed both glasses..with glass cleaner..

Dirt.
Open the ADF, the top of the scanner/copier.
The ADF glass is the thin strip of glass on the left. Damp cloth with windex or any glass cleaner. Scrub the strip of glass.

Your printer green cartridge drum cleaning blade is weak.you change it than solve it

The line was not a crack in the glass-as I thought it might be.

However, I cleaned the two sides of glass with piece of clean kitchen roll and it is clear now!

Thanks

J Taylor

is it wavy? if so then it is either the toner cartridge or the fuser unit (heat section) I would go for the fuser unit as the hot roller that makes the toner stick to the paper is only a plastic film. Have you noticed any gray pieces of plastic coming out?

Hope this help you and you can get these machines repaired also please rate me
Cheers J