The mesh is the Z-Wave mesh that the thermostat uses to communicate with the hub. If the mesh is weak it can lose packets and if the SmartApp isn’t aware that it’s losing packets then assume that the command succeeded and wont’ sent it again. Some SmartApps are specifically designed to have a closed loop and verify that commands aren’t lost the in the mesh, such as [RELEASE] Mode Based Thermostat - Control Multiple Thermostats Temperature / Remote Temperature Sensors when Changing Modes and [RELEASE] 5-2 Day Programmable Thermostat Scheduler (Weekday, Weekend) with Remote Temperature Sensor for each Schedule
The auto mode is the auto changeover option. The Honeywell T6 thermostat supports Auto Changeover. This makes the thermostat switch between Heat and Cool modes automatically so you don’t need to do it manually or through an app. It’s disabled by default but you can use a enhanced thermostat device handler which support this model to enable Auto change over and then it should automatically switch between heating and cooling based on the setpoints: [RELEASE] Enhanced Z-Wave Thermostat Device Handler with Z-Wave Plus