Bit new to the 3D printing lark myself but I’ve just overcome a similar problem where the printer wouldn’t remeber the z offset after reboot and print 19m above the build plate.
What I did may not work for you but I’ll share none the less.
I needed to use an old version a Cura (15.04.6) and re-upload the firmware. I don’t know why this worked but after the fact, I completed the Z calibration -> autorestart -> Auto level -> enter z offset, and everything worked fine. I even gained the +/- 0.1 feature which I never had before.
The usual, proceed at your own risk and make sure to use the firmware applicable to your machine malarkey:
- I tried option 3, Anycubic Kossel Auto Levelling (from the firmware link below)
- I studied the included PDF relating to the upload process
- My printer’s auto level switch best matched the version 1 image
- I then proceeded to use the Anycubic Kossel Plus Hex file with Cura 15.04.6
I was a little cautious as having done firmware on Arduinos you can quite easily brick them, but it all went smoothly and works as expected now.
Some things to look out for, make sure you use the correct comm port as indicated with in Windows Device Manager or your Mac alternative, and use the Baud rate stated in the Kossel handbook, auto didn’t work for me.
Other than that, best of luck!