Nighthawk M1 - loses mobile broadband connection when not used

Hi,

I use this device as a failover on the network if my main fibre is unavailable (not often).

At the moment it works OK, but if left to its own devices it loses the mobile data connection and a reboot is required to restore it.

Anyone have any ideas on why this happens - or any work arounds to keep it awake apart from connecting a smart plug an power cycling it every hour.

Thanks

Gavin