Ill give you an example of a ring main fault I came across a while ago this will reflect the concerns of the members im sure they are not having a go but just trying to help , as you, a consumer unit upgade , did the initial testing found open circuit on what appeared to be a ring main changed the board tested all the other ciruits and came back to the ring , so doing the basic visual tests as you would during an EICR opening up a few sockets all had 2 cables in I did end up taking off every socket in the house only a small bedroom so not to difficult what looked like to radials was infact a ring main ,the testing of both of the ring cables made it look like radials , insulation readings at 500 volt was above 500M so all appeared to be radials , so testing using the r1r2 I went round each socket testing till it went open circuit did this on each leg both stopped in the lounge , how it happened im not sure but one leg of the cable was cut in half enclosed in the wall under the capping , how I eventually found it was be tracing the cables in the loft as they all dropped down , I could see the link between the sockets but there was no continuity , so I just pulled the cable out of the capping and at the socket in the lounge pulled the other end of the leg out of the capping at the socket , luck was on my side as I managed to pull a new leg down the capping JB'd it in the loft and ring was back in action , another one I found was two cables coiled up in a back box never connected been like it for over 40 years so you can see the reasons ill post a pic of a cable after lights were lost and a spark just connected up the circuit from a ring main via a fused spur this will high light why you need to find the fault
