A1 nozzle scratching plate and damaging heatbed

My A1 is failing to complete any prints or even a bed level calibration.

The nozzle keeps scratching the lower part of the building plate during the leveling process. Some surface of the building plate is milled off. Nozzle also fails to know the upper boundary of the building plate, casuing the nozzle hitting the heatbed badly.


Footage of the printer trying to destroy itself during a bed leveling

I have tried

  1. Factory reset
  2. Disassemble and reassemble the machine
  3. Bed tramming described in A1 Bed Tramming | Bambu Lab Wiki
  4. Belt tensioning described in A1 Belt Tensioning | Bambu Lab Wiki

But none of above is helpful for preventing the nozzle from scratching building plate.

Another fact I have notice is the downwards movement in z when y is maximized. My printer lowers the nozzle when the heatbed is moved to the upmost position, ignoring z limit and causing interference. I cannot understand the logic of this movement. Can anyone test on their A1 to confirm the z change when y is increased to max?

The only reasonable explaination is that the printer may reduce z when x is minimized for pooping. However, my printer does not change z when x is set to both ends. It would be really helpful if anyone can test and report the z movement on their A1 when x/y is set to min/max!

Another footage of me moving the toolhead along x/y is attached. Please note the downwards z movement when y is maximized (which actually caused another terrible scratch when I was filming with the other hand).