sounds like the voltage and stepper motor settings in the new firmware have changed.
No clue on the bltouch, but changing firmware will usualy bugger something up :-)

I always try and avoid it.

Also bear in mind that the z-offset can be changed from the slicer.
Maybe it's not on 0.

There is no absolute 'right' or 'wrong' for this kind of thing. The 'correct' settings are the ones that work :-) Not necessarily the ones it claims in the instructions.