I also purchased just the cutting module kit. Unable to calibrate, error right when it starts calibration (lowering bed). Unknown error 0300-404c081801
I would try to take the blade out of the blade holder and put it back in. I say this because I got the same error, changed blades and it went away. I then went back to the original blade later on and that seems fine as well.
Unfortunately, same error after changing to a new blade (unable to calibrate, error right when it starts calibration (lowering bed). Unknown error 0300-404c081801)