Sounds more like a wifi issue as the Sh2 was fine. You could get your own router and wireless kit and stick the Hub in modem mode to get away from its wifi (as I have done with my SH2).
Or try this experiment and see if it stabilises things.
Go into the Hub3 settings. Type in http://192.168.0.1 into your web browser’s url box) and login with settings password on the Hub's base sticker (or your own if you changed it). Then in Advanced>wireless>signal disable "channel optimisation" – click apply changes. Then, go to advanced>wireless>security, rename the 2.4 & 5 GHz network ssid's in the boxes. Just change 'em to whatever you like and something that will differentiate them (e.g - xxxxx2 & xxxxx5) -- use the same password if you like, Then, apply settings and restart the Hub. Your 2 wifi networks will now be clearly separated - and you can then select the network you want to connect to individually from the "available networks" list on each device. 5 GHz is usually better and subject to less interference (and is better for iDevices ) than the 2.4 one - although this one has the better "range" and some older/cheaper/dumber devices can only use this one. Also use a wifi analyser App to check which 2.4 channels are being heavily used around you and move yours to one that is least so. See if that helps - you will lose any “seamless roaming” benefits but it may not matter and you can always change the settings back or do a "factory reset" if you prefer the way it was - or it doesn’t help.
-------------------- John --------------------
My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.