[Oldcodger]

Looking back at original post. OP states that master sockets have been used to fit extensions . Ring trip is a well known problem with more than one master socket. And from what OP describes ,it sounds like Ring trip is the problem
Only cure is to remove the capacitors and rewire the property using three wires from the master socket ( BT MAIN SOCKET ) to the rest of the house. The wire pairs should be ( for OP info, not those of us who know how to suck eggs) speech pair =blue pair ( blue wire with white marker and white wire with blue marker ) , and an orange pair ( orange wire/white marker+ white wire/orange marker). The purists in wiring will say only one configuration is correct, but as long as OP sticks to same convention at all sockets, then it matters not. I'm not a purist, but like to make life simple, so I stick to the convention of colours high, and use the blue wire with white to pin 3, with whitewire with blue to pin 2 , with the orange wire/white marker to pin 5.
But of course , the easiest way to prove that house wiring is/is not the problem is to try locating the main phone in the BT line side of the BT master socket. This is done by removing the lower haf of the BT master socket ,thus revealing the BT plug in the main body. Plug a phone in there( if BB goes to a Wi Fi router, use a filter at this point) and if fault goes- it's internal and BT will charge to fix, as mentioned in post #20. And don't rely on BT blokes ( I hesitate to call them engineers these days ,with current level of training) to know that the internal socket on a master socket is solely connected to BT. I had one bloke turn up to a fault one day. He didn’t know that the recessed socket was connected to line. He thought that it was connected to internal wiring and tried to charge.