Yet another Z-Height Issue

Not exactly sure what has caused my issue and have been struggling significant portion of the day trying to resolve this myself, but I am at wits end.

Issue is my Bore Setup in causing the spindle collet nut to bottom out at top of the work surface, 19.05mm (0.75") MDF.  I homed all axes, no issues where Z's home is at uppermost travel position.  Jogged X, Y, and Z to work surface to establish 0,0,0 via "Touch Off".  Setup "Bore" for 15mm hole depth, Bottom Height is Hole Bottom, no offset.  Top Height is Stock Top, no offset.  Tool is 3mm Ginmitsu flat end corncob mill (MC40A), OAL 37mm, length below holder set to 20.6375mm (13/16").  The boring starts as expected at the stock surface top but isn't stopping at the expected 15mm depth.  I checked the Design, and the negative extrusion looks good.

What am I missing?  Could it be the Step Scale for Z?  I changed that last weekend from 160 to 400 based on advise from PrintNC Discord discussion and dip switches on driver for Z.  I am reverting back to old settings and see what happens.  Honestly I have no idea what leadscrew I have, so uncertain the correct step scale setting. 

Figured it out. Z-axis stepper drive dip switch setting. Went back to previous settings, all is good.