Geofencing strange behaviour?

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Recently installed basic Todo system controlling Combi boiler (Vaillant). Have not subscribed to auto-assist. Tado App installed on 2x iPhone XR running iOS 15.2. All recommended settings for accurate geofencing have been set. Single Smart Schedule set up for during the day and home and Away Temperature set to 18degC.

When we (both) drive away "sometimes" we get a message such as 'you are away would you like to set .......... '. But usually when we are several miles away from the property.

However, when we are away, the thermostat sets itself to 18degC. At the same time a 'button' also appears to set geofencing ON. Switching it on or off makes no difference. To return to the Smart Schedule we have to press .... 'Return to Schedule' when we arrive home (ie: nothing more happens automatically).

Have I missed some vital setting?

Is this a normal behaviour?

Can anyone shed any light on what's happening?


Kind regards