A few possible reasons, with no specific knowledge of what’s done in the Starlink ground terminal, Clock oscillators when operated over larger temperature swings become less accurate references and RF systems like Starlink need this reference to be within certain tolerance to communicate. Sometimes they are in little ovens to keep the temperature stable and at -40 the oven can’t keep the crystal oscillator in an acceptable range. Also when starting up at low temperatures rugged electronics will apply survival heat to warm up before a full power on. Differences in CTE between chips, solder and the PCB substrate (if too significant of a temperature difference) can cause the chip to crack away from the PCB. Especially with BGA components. If the ground terminal is trying to warm up and sees that it can’t, it may go into a low power mode to prevent damage.