I was experimenting with the M98 sub program call. I inserted a "call" to another program on the USB (program is 10.nc). At the end of the "called" program I have M99, which should return to the main program after the M98 call. It doesn't. It looks like it returns to the beginning of the main program (which promptly runs the M98 again, sticking me in an endless loop). I've attached the main G-code as well as the referenced called program (10.nc).