Deco 3 disc home network periodically becomes increasingly unreliable and then fails entirely. App switches from normal operation to showing its opening 'set up your new network' screen. If I set up with my existing details the app tells me the network already exists, but the discs are in setup mode and I can't make my existing network work again.  What's wrong with it?

 In the account tab the network is showing, and it's connected, but the discs have the flashing blue light and there's no home network activity.