On setting that can cause that is the THC Corrections in MACH. There is a MIN and MAX. It sets how far in ABSOLUTE distance the Z can move during THC control. If you have the Min set to a positive number it will adjust up just fine but never let it come back down. Set the MIN value to -.250 or to turn it off set it to -1.00. It's there to keep the torch from running over a void and trying to lower voltage by lower the head down too far.
So as it climbs out of the cut what happens to:
1. The voltage display (should be going up)
2. The UP down LEDS (Down should be one if the voltage is going up (higher)
3. The Z motion based on the UP and DOWN commands
Anytime the UP is on the Z should be moving up. Any time the DOWN is on the Z should be moving DOWN. The Z DRO should be tracking.