We operate 2 iPads via our BT broadband.
They work fine for a short while - then stop connecting ,although the three sector wireless symbol at the top of the iPads is strong - and in settings the hub code has a tick next to it.
We have to forget the network - then reinput the wireless key and they start working again for a short while - then the process has to repeated.
Some devices have a problem with the Homehub dual band having the same SSid (name). You should try splitting them.