Continual Failure of Hub 3 to allow devices to connect

have been having problems for months with Hub 3 not allowing devices to connect. Can usually be resolved by restarting the hub, but then another device in the house is no longer connected.  This is driving us all mad. Particularly affecting two MacBooks of very different ages, whereas phones tend to be ok, but then one of  the tis in the house usually stays offline.  We've actually had a replacement Hub 3 a few weeks ago when an engineer came to visit after a network problem left us with other issues but this hasn't altered our internal problem.   I really wish I could just get out of this contract as it is causing us such a problem...   For example, i've been sat here for an hour now, after a problem this morning and waiting on an online chat which then failed.   Totally fed up with this. Haven't got time or mental energy for it any more.

Apologies - I couldn't edit the original post so I had to copy it to edit it - as you can see, I'm so frustrated, I was rushing to get it posted.

Twice the DHCP server has failed on our HUB 3 and the effect of this is network sockets & Wi-Fi both look to be working but devices fail to get an IP and then don't work.

The fix of the DHCP server on both occasions has been : 

1) Press RESET for 60 seconds.
2) Leave the Hub 3 powered on to revert to the factory settings.

Note : Restarting the Hub 3 and rebooting it from the admin menu were not a fix.