Z-Axis passes home position at end of job

Hi - I’ve having a “weird” problem in that I have a Z-Axis limit/home switch at the top of my Z-axis which works fine when homing my laser, but at the end of a job it overshoots the limit switch upwards and then moves down to the correct “pre-job” position following the overshoot. This isn’t great for the limit switch as it gets pushed further than it’s meant to go. I can implement “hard limits”, but this then alarms and I have to re-home again. I also notice that there is a “reverse Z direction” option in device settings - is this independent of GCode $3 ?

My controller settings are as follows:
$2=0
$3=5
$20=0
$21=0
$22=1
$23=3
$24=25.000
$25=800.000
$26=250
$27=1.000

Any ideas?
Thx John