HP Neverstop MFP 1200w Drum unit issues

I had bought a HP Neverstop MFP 1200w and started using it in Oct21, it came bundled with default drum unit and got some special offer where I got 2 free reload kits (103A)... (that tempted me and printer reviews were nice too)

Now, we have been printing/copying/scanning consistently every week since then, yet, the toner level indicator didn't fall ever! A year ago, I thought it might be some temporary error in default drum unit (104A) that should go away naturally, even had shaken it and reinstalled... cleaned the pins... the level LED simply doesn't fall!

But it seems now that I can only print once a single page, then the printer goes into all sorts of noises and throws error codes if given to continue like this for 3-4 mins (soln. reseat the drum unit) after which I power it off and take the next single print... same for copy.

According to data I still have 13k impressions left on the drum, I know the toner level has gone low, but the system doesn't let me reload toner as it reads full always (I may break the plastics if forced)...

Anyone has a solution? Have faced similar issues? Shall I buy a compatible drum unit (approx 2-3k on FK/AZ) and test? New original one costs 6k, printer was worth 17k when purchased...

* Please tag techies at DD if you know them *