Print documents streaked, discoloured, off-centre, enlarged

[AlexKivial]

Hi everyone, I have an HP M501dn which has never given any problems until now.

But lately when I send documents to print, it very often happens that some pages are printed enlarged or ‘stretched’ as well as discoloured and off-centre with respect to the sheet, I have noticed that this is more frequent in prints with more pages.

This is the list of tests performed (not in chronological order):

1. Removing the printer from the devices and reconfiguring (on two Windows PCs).
2. Updating the printer firmware to the latest version (I installed v.20240807)
   https://support.hp.com/it-it/drivers/hp-laserjet-pro-m501-series/model/7837163
3. Updating the printer drivers both on MacOS 10.14 (I chose ‘Install HP Easy Start v2.15.0.240923’)
   and on Windows 10 64bit (I chose ‘HP LaserJet Pro M501 Printer series PCL-6 v4 Full Software and Drivers v18.0.19228.302’, maybe I need to use the basic ones)?
   https://support.hp.com/it-it/drivers/hp-laserjet-pro-m501-series/model/7837163
4. Resetting the printer to default settings (both from the screen and from the remote ui) and reconfiguring on the network.
5. Replacing the network cable from the printer to the wall port (I thought it was faulty).
6. Printing test with the ‘print as image’ flag from the Windows UI
7. Test printing at actual size without scaling/adaptation/rotation
8. Print test from multiple software (word/acrobat/foxit pdf reader/...)
9. Print tests on multiple documents, both on the server and locally on the computers.

These are additional notes and/or details:

• From what I've noticed, the problem is on both Windows and MacOS (on this one, however, it seems to have been resolved after updates).
• The problems started pretty much since the last cartridge replacement (but I doubt it has anything to do with the problem).
• Trying to print from another MacOS on the network to that printer still hasn't given me any problems (I haven't changed or updated anything on this MacOS).
• I have noticed that when a print job is completed, the ‘Print Document’ status returns on the display even if there are no documents in the queue (you are bound to cancel it from the printer's physical button).

I hope someone can give me some useful advice!

Maybe I'm missing some important detail and have the answer right under my nose....

Thank you all.

Best regards, Alex.