Your post is a bit confusing to me so let me explain a few failure modes:
1) Z never ever goes up. Always down.
2) Z goes wrong direction. When you try to home it goes all the way down and makes bad noise.
3) Z moves wrong distance (usually half) so when you home it from the bottom it never reaches the top - if you home near the top it homes properly. When you print things they are half height.
4) Z works fine usually but sometimes bed falls suddenly for no apparent reason (this is normal - steppers turn off after a minute of no use).
5) Z moves one direction but refuses to move the other direction (limit switch problem).
Is your problem one of 1-5 above? If not maybe a video will help as the words you wrote don't make complete sense in English (sorry!).
Even better. Forget about the calibration thingy.
Do Prepare/auto home
Then move the hotend to the basic 3 corners and make the nozzle 'kiss' the bed slightly.
That will calibrate the hotend to 0. Repeat front corners after adjusting the one on the central back of the bed.
Also you can get a feller gauge and after doing the home, go prepare/move axis/move 0.1mm/move z
To move the bed just 0.1
This way (with a feller gauge you can 'fell' if the gap it's really 0.1 when calibrating the bed screws.
After an autohome x/y can be moved by hand, but Z motor will be blocked (so you can do this operations). To unlock it use Prepare/Disable steppers
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