Same problem too. Sometimes sensors doesn't reconnect to network. I experimented it mostly of the time with sensors connected to repeater. I also added a status LED to check if repeater is still running (heartbeat) and it does. It seems all my sensors are still running (i can check it with my actuator button, if sensor is not connected and i press the button sensor does nothing while if it is connected to repeater it switches relay properly) so i guess my sensors are still connected to repeater but repeater seems not to be connected to gateway.