Poor copying quality on LaserJet Pro MFP M125a

[Niimy]

Hello , I have been trying to fix an issue with my multifunction printer to no avail.

I own a LaserJet Pro MFP M125a, connect with a USB (no Wi-Fi connection) with a LED controller.

The issue: copying quality has severely decreased (on a plain black text print), the copy isn't blotchy or streaky but instead letters appear faded in certain areas and with a mostly light gray tone (this issue appears even when using the maximum darkness allowed on the LED controller, 4).

I have done two fresh installs (unistalled all HP related programs, ran printui.exe /s and removed the device, ran c:/programdata and deleted all HP related files/folders and rebooted before doing each install). I installed the latest recommended Driver-Product Installation Software (released March 5th 2021) and updated the firmware to the latest one aswell (released January 28th 2021). I have also done the standard reset by unplugging the cables waiting 60 seconds and replugging.

Other tools used:

HP Device Toolbox to restore copy default (optimize: text, paper size: A4 and paper type: plain). I used the cleaning mode to make ensure that the printer is clean. Test pages print optimally.

HP Support Assistant says my printer is fully updated.

HP Update couldn't find any new updates either.

I installed the latest HP Print and Scan Doctor for Windows  (released December 9th 2021) and ran it. It tells me "a later version of software is available for this product" and links me to the page where i downloaded the latest update. I also ran the portion for "finding and fixing scanning problems" where it showed checks for: "Recommended Updates", "Device Manager", "Device Status", "Windows (WIA) Scan" and "HP Scan". Note that scanning only has no issues the scan is nicely colored and crisp, the issue is only when copying (scanning and then printing).

So to summarize it: printing has good quality, scanning has good quality, printer was reset and had a fresh install (two in fact), printer is fully updated and the diagnostic tools couldn't find any issues.

I'd appreciate any help on what else I can do to fix this.

Thank you in advance.

[Repairatrooper]

Copying and scanning use different imaging algorithms and sometimes copying is too sensitive to dirty and debris on the scanner glass. If you have an ADF and glass do the copies look the same from both? If yes you may have a hardware issue, if not then you need to make sure you clean the slit glass that the ADF uses when it scans. 

[Niimy]

Thank you for the quick reply.

To be a bit clearer, although I'm not sure on specific the terminology, my printer only has manual scanning/copying (one page at a time onto a glass scanner), so the only feeder it has is for the printing paper portion. There is no automatic feeder for scanning/copying, not sure if that matters.

Just to be safe I cleaned the surface of the glass scanner and the result remains the same.