While not a NetFabb user (yet), the solution to your issue seems spot on. If you don't have issues running the print with the 0.75 but do when using 1.0, then I would agree that the software is just not displaying the value correct.
Does NetFabb output a file you can open in brackets? If so, maybe you can check the output file.
Another way to know would to be SSH into the printer and check the printer settings once the job is loaded.