Congrats for perseverance in this matter, Walter.
But, this reads to me as proof-positive that "Just having a profile reset - banding removed", by way of a phone call to the ISP by the EU, is definitely not the way forward. Well done Zen/BT for refusing to perform the reset without an actual engineering visit. That way, the real-life fault (capacitance imbalance) was located and repaired, and only then was the reset carried out, with the knowledge that it is highly unlikely the DLM will re-apply a banding any time in the near future.
Just keep hitting the reset button is not the answer, there is usually a reason behind the DLM's actions. Granted, electrical storms and other extreme high-noise bursts can disrupt the DLM on an otherwise perfect circuit, but these will be in the low percentages.