Here’s something you can try—it worked for me when I was dealing with spurious errors.
What I’m about to describe defies logic—except that it was the only thing that worked for me when I was getting a similar error claiming the toolhead cover had fallen off. I spent over $100 on parts trying to fix the issue, and nothing worked. Then, on my 20th attempt, I left the screws out of the back cover, expecting I’d need to remove them again anyway.
After a week of flawless printing, I reinstalled the screws. The problem came back immediately. I removed them again, tested, and the problem disappeared. I repeated this process five times and was able to reproduce the error every single time. So now, I run the printer with only the bare minimum of screws to keep the cover in place.
I was pissed at all the money I wasted. This was one of the few times I actually contacted Bambu Support, and they completely failed me. On top of that, they bullied me into upgrading my firmware—even though I explicitly told them I didn’t want to. They flat-out refused to answer any more questions until I upgraded. Once I did, the issue persisted, and I was locked out of back-revving because Bambu’s attitude is basically “Pound sand.”
Here’s what my printer looks like now—trouble-free ever since:
I have no screws in the center shroud, it is only held in place by friction and clips. My theory is that the PCB may come under stress and as a result, the hall affect sensors were being mechanically stressed or the PCB was being stressed. Your error may be suffering from something similar. It’s worth a try.
To borrow from Sherlock Holmes:
“When you have eliminated the impossible, whatever remains, however improbable, must be the truth.”