Not sure if I am making progress, but I at least have traced the line from one end to the other. We had this tracer kit in our tool kit:

https://www.amazon.com/gp/product/B01HCQSHNG/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

I set it up in Scan mode, plugged into the jack at the phone location. I used the tracer and the tone was clear at the TVA50 end of the run. So at a gross level the line is continuous. Do I try testing each individual wire in the 2 pair (4 wire) line to see if one is loose or broken?