Manual Thermal Model Calibration fails when connected

[curieos]

I had to replace the thermistor in my MK3S, so I thought it would be a good idea to re-run the thermal model cal. When I select it in the menu on the LCD, it homes, moves to the position to start the calibration, and then calibration fails due to the printer being "Not Idle". When I disconnect the Pi and select it, it starts fine.