I’m running into this issue too. I tried all of the things other people have above.
To add to the discussion: I also traced the cancel (emergency stop) button to pin 1 and 6 of the button board cable. I confirmed that pressing the button zeros resistance between these two pins. With the cable connected I traced the circuit board pin headers between both sides of the cable to rule it out as the source of the problem (connection on both pins across the cable is good).
Possibly related is that the Cancel / Emergeny Stop button has never worked so I’m suspicious now that it’s something wrong on the mainboard.
I have an open ticket with Bambu and I’m within 14 days of purchase so I’m hoping this will all work out. Did anyone else on the thread have any luck resolving this?