Think I may have found the solution!
Increasing the softDelay() times in your goToSleep() fixed it:
void goToSleep() {
fuelGauge.sleep();
Particle.disconnect();
softDelay(5000);
Cellular.off();
softDelay(5000); // Step through the process safely to ensure the lowest Modem Power.
System.sleep(doorSensor, CHANGE, 7200);
softDelay(5000);
}
Magic…