[Biggyboy]

I don't see anything wrong with the code. Maybe it's a Mach3 issue?

Can you post the code that runs OK so we can compare the two?

Its the exact same string of code, only difference is I did not include the other two rows of slots in the tool path.
So If I run the tool path to only cut the center row its fine, only when my tool path includes all three rows, does the center row miss steps in the same location and depth.
ger21 says about a Mach3 bug that can cause the acceleration to over shoot.

(SLOT5)
M5
T17 M6
S16000 M3
G54
G0 X532.516 Y59.5
G43 Z15. H17
G1 Z5. F2000.
Z2.5 F230.
Z-3.
X589.816 F2000.
Z-6. F230.
X532.516 F2000.
Z-9. F230.
X589.816 F2000.
Z-12. F230.
X532.516 F2000.
Z-15. F230.
X589.816 F2000.
Z-18. F230.
X532.516 F2000.
Z-21. F230.
X589.816 F2000.
Z-24. F230.
X532.516 F2000.
Z5.
X465.014
Z2.5 F230.
Z-3.
X503.516 F2000.
Z-6. F230.
X465.014 F2000.
Z-9. F230.
X503.516 F2000.
Z-12. F230.
X465.014 F2000.
Z-15. F230.
X503.516 F2000.
Z-18. F230.
X465.014 F2000.
Z-21. F230.
X503.516 F2000.
Z-24. F230.
X465.014 F2000.
Z5.
X417.014
Z2.5 F230.
Z-3.
X436.014 F2000.
Z-6. F230.
X417.014 F2000.
Z-9. F230.
X436.014 F2000.
Z-12. F230.
X417.014 F2000.
Z-15. F230.
X436.014 F2000.
Z-18. F230.
X417.014 F2000.
Z-21. F230.
X436.014 F2000.
Z-24. F230.
X417.014 F2000.
Z5.
X222.064
Z2.5 F230.
Z-3.
X387.536 F2000.
Z-6. F230.
X222.064 F2000.
Z-9. F230.
X387.536 F2000.
Z-12. F230.
X222.064 F2000.
Z-15. F230.
X387.536 F2000.
Z-18. F230.
X222.064 F2000.
Z-21. F230.
X387.536 F2000.
Z-24. F230.
X222.064 F2000.
Z5.
X173.586
Z2.5 F230.
Z-3.
X192.586 F2000.
Z-6. F230.
X173.586 F2000.
Z-9. F230.
X192.586 F2000.
Z-12. F230.
X173.586 F2000.
Z-15. F230.
X192.586 F2000.
Z-18. F230.
X173.586 F2000.
Z-21. F230.
X192.586 F2000.
Z-24. F230.
X173.586 F2000.
Z5.
X106.084
Z2.5 F230.
Z-3.
X144.586 F2000.
Z-6. F230.
X106.084 F2000.
Z-9. F230.
X144.586 F2000.
Z-12. F230.
X106.084 F2000.
Z-15. F230.
X144.586 F2000.
Z-18. F230.
X106.084 F2000.
Z-21. F230.
X144.586 F2000.
Z-24. F230.
X106.084 F2000.
Z5.
X19.784
Z2.5 F230.
Z-3.
X77.084 F2000.
Z-6. F230.
X19.784 F2000.
Z-9. F230.
X77.084 F2000.
Z-12. F230.
X19.784 F2000.
Z-15. F230.
X77.084 F2000.
Z-18. F230.
X19.784 F2000.
Z-21. F230.
X77.084 F2000.
Z-24. F230.
X19.784 F2000.
Z15.
G28 G91 Z0.
G90