Hi John,
Very nice looking machine.
You are using the latest / best version of Mach3.
There is something not quite right dimensionally with your Gcode file but I am not clever enough to spot where the problem lies. I suspect that Mach3 thinks there is not enough room to apply the cutter radius compensation (lead-in) so it takes an alternative path.
Incidentally UCCNC also reports cutter radius compensation warnings when your Gcode file is loaded which may confirm a Gcode dimensional error is present.
Tweakie.