If possible please send the sample NC Rout/Mill file that is not correct, and I'll attempt to load into FAB3000.
What options are being used when exporting to NC Rout/Mill?
Have you tried importing the NC Rout/Mill files into any other Free Viewer or CAM software (to verify)?
Note: The NC Rout/Mill file format is almost 50 years old, so when importing back into any CAM software - it's important to enter back-in the same NC Rout/Mill format information (leading or trailing zeros, digits: integer and decimal, etc.) For more information about loading Drill files,
Benoit Losey