Auto bed level Z offset inconsistent

[DBFIU]

Oh Wait! The Z_PROBE_OFFSET is only used at the end of the G29 when it 'Corrects' the nozzle position. That M851 command won't do anything unless you do a G29 also. And of course, you don't want to do that in a middle of a print.

Yea I was wondering why it wasnt actually adjusting mid print.

Can you take a look at my pre gcode script and tell me if it somehow fudges something up before a print?

I use simplify3D exclusively.

G21 ;metric values
G90 ;absolute positioning
G28 ;move to endstops
G29 ;allows for auto-levelling
G1 X150 Y5 Z15.0 F3000 ;center and move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F300 E30 ;extrude 30mm of feed stock
G92 E0 ;zero the extruded length again
G1 X175 Y25 Z0 F3000 ;remove bugger
G1 X200 F3000 ;remove bugger
G1 X150 Y150 Z15 F3000 ;recenter and begin
G1 F3000