I was donated a MINT Canon 9000F Mk II Flatbed Scanner a couple of years ago to replace my Busted Epson 1650 -- it was lovely ! Great for Medium Format as I n ow have a Plustek OptickFilm 7200 for 35mm so use that as I didn't want to 'wear lout' the Canon --- suddenly it has a 'blue area ;' down one side and 'scan lines' appeared, spoiling my Club Competition and Forum Photos . I have tried cleaning the glass and wiped the glass of the strip light -- nothing works HELP PLEASE !!
never saw this issue, but looks like you may not be alone... https://community.usa.canon.com/t5/...-Mark2-Dark-stripes-on-every-scan/td-p/255482 Indicates that others had issues, and that unplugging everything and toggling the lock switch a dozen times could somehow fix it. I am skeptical but i guess its worth a try. https://www.fullypsyched.com/calibrate-canoscan-scanner-remove-lines/ makes me think there may be a calibration option for your scanner that could also possibly resolve it, that link is not specific to your scanner but may be worth looking into as well. These are a few starter thoughts at least.
YO !!! I tried suggestions such as 'Toggle Lock Switch' then in Vuescan under 'Scanner' clicked on 'Calibrate' and at first the 'warm Up Lamp' went to 100% but NO PREVIEW so I switched everything OFF and ON again and clicked on 'scan' and suddenly scanner creaked into ACTION and NO MORE SCAN LINES ! So RELIEVED !