btw, q: The 'loop' is I take it just the normal copper pair? Or something else?
Yes, the normal metallic pathway, the copper pair. I used quotation marks around the phrase, "Loop (Rectified)", which I copied directly from the system message that you showed in an earlier post. That phrase is a little ambiguous . . . it could be implying that with every item of CPE disconnected from the circuit the pair was still showing as looped (low resistance, A-wire to B-wire) and that semi-conductive tendencies were also detected.
Having now read all of your following posts, I am guessing that the semi-conductive joint was up on the moor and the low resistance, A-wire to B-wire, was an artefact of the dying face-plate or of the dying NTE5. (I don't understand the comment about the face-plate "containing a capacitor" . . . because it doesn't! The back part of the NTE5 contains a series connected 470 k Ohm resistor and 1.8 u Farad capacitor that shunt the pair.)
Hmm . . . Also found a battery contact fault. I'm beginning to think that an induced surge, from earlier atmospheric electrical discharge, had caused the damage.