Smart Hub Plus - digital phone dropping

[Roger84]

Moved form BT FTTP where we already had digital phone with BT handsets.

now on EE with Smart Hub Plus and the same BT phones paired to the hub.

digital phone keeps dropping out.

When in the “broken” state I can get the dial tone, dial a number and it appears to connect (timer clock starts) but voice does not transmit and nothing in the earpiece. 
If you call the landline number, the phone rings, you connect but again no audio either way.

hub reset fixes it but you have to constantly check you have service.

Any ideas? It was flawless with the BT Home Hub2!

[Shires999]

So as an update, a hub reset only really cured the problem for a day or so. So I did a full reset of the open reach modem by fully switching off the power to it for about an hour. That was two months and so far the issue hasn't come back again.