I am using the Fusion 360 post processor and enabled Z control in the post options.  I am trying to get THC to work properly.  It seems that the Z axis doesn't want to go below the Z height set in the G code. Does anyone know if this behavior is what is expected or am I looking at a different problem?  The Z seems to hang around 0.6, but not exactly (within a few hundredths).  Thanks for any insight.

Example:
N10 G90
N15 G70

(2D Profile1 2)
N20 G0 X-0.0468 Y4.5332
N25 G0 Z0.67
N30 G0 Z0.07
N35 M3
N40 G4 P1.
N45 G1 Z0.06 F20.
N50 G1 X-0.0427 Y4.6031
N55 G1 X-0.0476 Y4.6033
N60 G1 X-0.0528 Y4.6035
N65 G1 X-0.0582 Y4.6037
...