Ever since I start to use the heating, roughly every two weeks, my furnace fan continuously running even furnace turned off. It does not happen every day but like every two weeks. When I restart the Nest thermostat then the fan stops. HVAC technician already came several times and found furnace normal. They helped me replaced a new Nest, the issue still exits. I don’t have any fan schedule or auto schedule, airwave.etc all turned off. Online technician also checked the HVAC system as it is compatible with Nest thermostat. Plz suggest what would be possible issue. Wires pic attached. Thanks!
