@brucegage I have had this problem on every slicer and for me it has to do with the z steppers and layer heights. Not all layer heights print the same. I had a 0.33 and 0.35 fail, but the 0.34 printed perfectly.
Also, just for fun, check your x-axis belt tension and the pulley set screw on the stepper.
I have active licensing for most of the slicer programs available to work with.
If so, home your printer. Then, release the motor tension and move the head down so that the nozzle is touching the build plate in the center of the bed. Go to the LCD and set Z=0. Then Re-home the machine and run the leveling again. Should be back to normal.
It should load into MC without issue. Does it give you an error message?
Other software uses slightly different syntax in the gcode, so MC may not parse it for viewing the same way, but if you use the slider on the right and drag it all the way to the top, it should show you entire gcode in the 3D view panel
@pverdin This is likely happening due to curling which is why it happens once the overhang begins. I personally find success when I print PETG around 260c hotend and 75c on the bed with 100% cooing to prevent curling.