To be honest if it’s internal wiring within the walls, done properly, then there’s little chance of it getting damaged. In my field engineer days it was common in new homes fitted out with internal wiring to have some quite decent tubing within the walls, dunno about nowadays as it’s a long time since I was on the tools. Saying that I’ve attended lightening strikes where the wiring has been blown out of the walls and it’s been anywhere but straight..
If you leave the wiring connected to the master socket, but with everything unplugged from the sockets, phones, filters, extension leads, Skybox etc and try ringing the line and see if it’s still giving engaged or not. That way you have proved it onto the internal wiring or onto a device.
If you have Broadband ADSL and filters in every socket with a phone, then you don’t need the third wire (ringing wire/bell wire) and it’s a common trick to disconnect it from all the sockets to slightly improve the ADSL Sync speed.
Focusing on the wires on 2&5 disconnected from the line, using a multimeter starting off with it set to 240Volts AC (Good habit you never know when you are working on a fault where the line is in contact with the mains) then set it to something low on the resistance (Ohms) scale say 100/200 and see if it gives a reading, it shouldn’t if the wiring is OK, a short will most likely give a reading near to zero Ohms.