Connection issues

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I had had my system installed since 2018 with very few problems. Over the last 2 or 3 weeks, 2 of my radiator stats and the smart thermostat have regularly lost contact with the bridge. If this happens when at the end of an ‘on’ schedule the system stays on, wasting energy! I have replaced the batteries in all 3 devices and nothing has changed in the systems configuration. Any one else having similar issues? It takes a while to get the devices to link properly so that the system shuts down fully, sometimes I have to switch pairing on to achieve this. Could my bridge be failing? Has there been an updated bridge since 2018. Any ideas welcome. Thanks, Mike