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I cannot seem to make this work properly. After a mesh probe the z ends up WAY too close to the bed. Slightly pushing the bed down, actually. I've tried changing the z-offset. No matter what I set the z-offset, after probing it goes right back to where it was. Just to be sure I set the z-offset to 10 (M851 z10; m500). No change. It goes back the same it always seems to be. Setting the z-offset makes no difference.

Does anyone have an idea of why? My starting print G-code is:

G28 ;
M420 S1;
G1 Z15 F1000;
M107 ; fan off
G5 ; enable resume from power failure
G92 E0 ; zero E axis
G1 E8 F200 ; prime
G92 E0 ; re-zero E axis