Phone routed through Livebox cuts out after about ten seconds

[nectarine]

Another Livebox problem (collective groan from readers).  The outgoing line through the Livebox keeps just going dead after ten or fiteen seconds and only works again if I disconnect the Livebox and restart everything.  However going into the diqgnostics box says that the phone is working OK.  This has only happened in the last few days = there was a storm but I had unplugged everything =  and the phone works fine if it is connected directly to the phone socket outside the LBox.  Please don't suggest another LBox as I'm on my fourth in a year.

Everything else, internet connection works fine.  Help .