What is causing power failures with my comfortnet thermostat?

With very little info given I will take a stab in the dark. If you use electric heat it takes 230v to make the system work. If you have gas heat, rule of thumb you need 115v to make the system work. If main power drops going to the blower section you loose 24v going to the thermostat. The question is are you losing main power or 24v power due to a limit switch that is opening?

I am not losing main power. I sat with multimeter in hand and had little if no droppage of power. I was unable to check if there was a droppage of amperage. It is a heat pump, and has dropped power when running heat, my confusion is worsened when it does not happen all of the time. Like today for instance, I broke down and called the heat/ac repair people and have not been able to get the system to fail once. That is with switching from heat to cool.