Just downloaded your latest software, version 1.0.331. Just now trying it out on a grbl driven commercial Automove 303 which is calibrated in inches, 1000 steps/revolution. Your simulator correctly positions the 3D display in inch mode, but the RUN mode interprets the G20 commands as milimeters and only moves fractions of an inch in the lower left bottom corner while the spindle moves correctly in inches. Instead of showing 18 inches of movement, it shows 18 mm on the display. The machine moves correctly but the RUN display does not. What setting do I need to configure to get the correct display in the RUN mode?
Found Connect interprets $13 = 1 as MM instead of inches. Setting it to 0 solves the problem, but is incompatible with UGS that requires reporting position as inches to properly display. Connect needs to switch display dependent on the GRBL $13 settings. Work-around fixes problem, but requires changing GRBL settings depending on which sender is in use.