Try this, see if it helps. Do a pinhole reset to factory settings. Push the pin in to its stop point and hold for a "timed" 40 seconds do NOT restart the router after that. U'name & p'word will revert to those on the Hub's sticker.
-------------------- 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.
I've been having this exact issue, it's been getting increasing more frequent and is quite annoying!
I'm talking to chat support right now, but can only send a technician out in January.
Is it possible to just arrange a replacement hub to be posted? I'm chatting to a nice chap, but he doesn't really understand the issue, keeps asking me if the internet connection is intermittent, when it's just a hub issues, and he's said that the automated system won't allow him to send a replacement.