I have the same problem. Sometimes the the orange warning light together with the STOP is on and temperature is about 80 and sometimes the temperature gauge shows almost 100 and the light is off. Coolant level is OK, To make the orange light off during the drive sometimes helps turning on the heating. (but it is very unconfortable in summer) the STOP light is not only LHM fluid level. It also comes on together with others "fatal" problems.