FLSUN I3, Skr mini e3v3, tft35, CR touch. Marlin bugfix 2.0-x. Print came loose, causing damage to hotend. All fixed, but Z offset is messed up. Home on Z is now +2.2mm and cant go lower. M851 Z0 does nothing. can adjust the Z offset manually from screen, but its 4+mm, and test cube is 18mm tall, not 20. Any ideas?