OfficeJet Pro 8600 gives unhelpful "Printer Failure" error... but works fine in MFG mode?

[blanknam3d]

As stated in the title. I have an OfficeJet Pro 8600, it keeps throwing a "Printer Failure" message that just tells me to restart the printer, saying there is a problem with the ink system...

...Issue here though, is that I literally just completely cleaned up the ink system in this printer. I cleaned the printhead, I cleaned the inkhead cleaning tray, and made sure all the essential parts to it were working. I did a full reset in the firmware service menu of the printer, and it still didn't work.

But, what DID work is going into the firmware service menu, selecting MFG mode, waiting for the power button light to turn off on the grid screen, then powering on the printer. Seemingly, that makes it dismiss whatever the error is & makes the printer able to print regardless of any internal issue. The problem with MFG mode? USB is disabled, and I also have to manually re-enable it whenever the printer is restarted.

Even more so... the printer seems to print perfectly fine in MFG mode over Wi-Fi as if there were never any issues! No smearing, no leaking ink, prints perfect colors! So, what the hell is this printer's issue that makes it unable to print when not started in a special firmware mode? I want this printer to be able to connect to my PC via USB & also not have to manually reset it every time I restart it, and as such can't just use MFG mode as the solution to my issue.

TL;DR: OfficeJet Pro 8600 is giving a vague "Printer Failure" error, but if you use a special boot option in the firmware service menu to ignore errors, it seems to not have any problems & print fine anyway. Why can't it print when booted normally, and why can't it just tell me exactly what the failure is, especially if it prints fine in MFG mode anyway?