Print an internal page (not sure how with this model) like a supplies page, a PDL page, a font page, or a startup page. Is ghe defect on this page? If not then it's a driver/software issue and not a hardware issue. You may need to reinstall the print driver or wait for a driver update.
I replaced my toner cartridge and drum a couple months ago. Since my Mac updated to Sonomoa 14, I get a large toner bar across the top 1" of the page. very frustrating, as even if there isn't anything printed in that area, it is still showing up.
I followed the instructions on how to clean it, and the cloth I was using wasn't coming back with extra toner, so I'm not sure what is causing the issue. Could it be that the computer isn't getting the right signal now that it is on Sonoma? Is there a way to clean the rollers in the back of the machine, after the drum?