The engineers will have used the TDR or Wheatstone Bridge on their meters to try and determine where your fault is. What I would have done then, is used a Cat & Genny to track the cable and a Pedometer to measure it. If your feed cable is
DIG (Direct in ground), then they will have to have the area exposed where they perceive the fault to be. Our contractors carry out the excavation work and will dig a 1mtr x 1mtr area. A 'Joint box' will be then put in the ground if it is feasable, so that no future excavation work is necessary.
Houses built in the 60's and 70's are notorious for having
DIG cables. The main 'Spine' runs down the street with 'Tee-offs' at each and every house. We call the underground joints 'Submarine joints' as they resemble a submarine, but they are awful to remove as they are resin-filled and form a solid block around the conductors. We therefore have to 'Buzz' each pair one at a time and connect through to a new strap cable that by-passes the old joint. As time has gone by, these joints are now beginning to break down and allow ingress of water, thus causing problems.
Try not to subscribe to Walters misery towards BT/OR renluop. Cheap plastic ducting wasn't available back in the day, and at the time the powers that be decided that DIG armoured cable was practical, cost-effective and served its purpose. Fast forward to today, and yes of course we use duct where at all possible which means no further excavation should ever be needed. I wish I had Walters 'Powers of hindsight' sometimes, there's lots I could complain about.