At a guess, I would say that the device you are using supports both wireless bands, and because you cannot rename them on the smart hub 2, your device is getting confused.
You could try turning off the 5GHz wireless on the home hub, and see if that helps.
The Smart Hub 2 is intended for use with the Complete Wifi Solution from BT, so unless you plan to rent the add on black discs, there is no advantage in using it, and you would be better off using the normal home hub 6.