2.1.1 Marlin and Arduino IDE.
I have an occasional problem during heat-up where it shuts down with a run away heat message.
I have the print temp at 200 and watching closely during heat-up, the PID lets it sometimes get down to 190 and it triggers. If it doesn't go below 191during that first heat cycle, it heats OK then runs fine.
I have done a few PID settings (M303 ...) between 200 and 220 but it still sometimes drops to that 190 first time around
I am guessing there is a setting within Marlin for a 10-degree difference but danged if I can find it. I found one setting
TEMP_SENSOR_REDUNDANT_MAX_DIFF 10
and changed that to 15, but no help.