Re-join after gateway's power outage

I am having an issue getting the LoRa CubeCell devices to reconnect after the gateway/app server is reset or if there has been a power outage. All the devices are running on OTAA and are in class A.

The setup is prety simple, The M02 has the devices registered and you can then start them up and they connect perfectly reporting the sensor data.

But if for some reason the M02 looses power then comes back up the devices do not rejoin, The M02 after starting back up seems to change the Device Address of the device and the device continues to send data using the Device Address that it had previously.

in the Packet Logger I can see that data is still comming in but its not being sent to the application.

I have not yet tested this but it could be a result of using LoRaWAN.ifskipjoin();

Does anyone have a way around this? or does anyone have any sugestions om how to detect if the sensor is not actually conected and then force a rejoin?

Thanks in advance for any help.