Different Probe Z offset for G28 and G29 After trying to solve this for the whole weekend I've run out of ideas.

I've fitted an BLTouch to my Ender-3 with an SKR mini e3 V2.0 board, firmware is Marlin 2.0. 

My issue is the following: 
when I do autohome (G28) it uses the Z-Probe (BLTouch) to home (this is expected). 
I then set Z Probe offset to 0 (using M851 Z0) and move Z down until it the nozzle touches a piece of paper.
I then set the Probe Z offset to whatever value Z is at (M851 Z-4.10), save the settings to EEPROM and restart the machine. When doing another G28 and moving Z to 0 afterwards the distance is perfectly the same. This is repeatable.
However when I do G29 it measures the bed to be sitting around -1.9&nbsp;mm, therefore moving Z to 0 will crash the nozzle to the bed. I can change my Probe Z offset have this fitting (M851 Z-2.20), however then the nozzle sits ~2&nbsp;mm above the bed when doing another G28 with "Bed Leveling" disabled. 

All of this is perfectly repeatable, so I think my I've got something off in my Marlin configuration, but can't find anything wrong. 

What I've tried so far:


Setting the Z offset as default in config -> this yields the same result as saving it to EEPROM  
Reflashing the firmware and resetting the EEPROM -> this didn't change anything  
Connecting the probe as Z-Endstop and as Z-Probe -> after matching the configuration (setting/unsetting Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN) it just gave the same result. 


Did anyone encounter this issue before or can give me any idea how to fix this? Any help would be appreciated.

EDIT: I've just flashed the precompiled stock firmware from the BTT Github and it works. So im quite sure i've got something wrong in my config. But since I can't find the configuration.h for that .bin file, I can't realy compare both
I'm answering my own question here. 

The Issue was that I set Z_MIN_POS to -2.0 I guess these 2&nbsp;mm were subtracted from G28 but not from G29.

I don't know wether this is expected behaviour but changing Z_MIN_POS back to 0 fixed the issue for me.