You probably have two issues:
1 - there is some play causing your values being inconsistent, or Z have lost a few steps during carving.
2 - you need to recalibrate your $102 value.
To solve or minimize 1) make sure your mechanic is solid and as stout as possible.
To solve 2) you for need to get a good measurement of actual travel.
Take a ruler and place it next to Z, jog it as high it will go and measure the actual travel and take note of that and what the commanded value was. Say travel is 150mm and commanded was only 100mm.
Current $102 value divided with actual travel multiplied with commanded travel
Say $102 is 200 the:
200/150*100 = 133.33 which is your new $102 value
You might need to perform this a couple of times to get it as precise as possible.
I’d add to the above suggestions that given how rough those holes look, you may be taking a too aggressive speed there and are missing steps on the motors? Your edges shouldn’t be that rough; they won’t be mirror finish like machining steel, but they shouldn’t look like a shag carpet…