Have HVAC Questions? Ask an HVAC Expert for Answers
This can be an issue with the thermostat or with the equipment.Do you know if the unit is hard wired for 24v power or battery powered only.Often weak batteries will cause this.so I would start by replacing batteries if they have not done so.
Our next step will require a volt meter to see if the thermostat is losing and sending signal when this is happening.
Let me know if you are seeing my reply.