I've reinstalled my original Openreach supplied flat cable and been more careful to route it away from everything else. (The various cables look
even more of a mess now.)
The downstream max rate hasn't changed significantly (hovering around 83000),
and the downstream path rate is still the lower value (70258 against 76179 before fiddling) (? DLM lowered rate after short bad periods with the other cable?).
However, my downstream RSCorr rate seems to have dropped very significantly.
Was around 60 per second before fiddling, went up to 200 per second with the bad cable, and now showing an average of 8.5 per second after 17 hours.
I don't know how much that is to do with the slower speed from a more conservative 6.5 snr against around 4.5 before
Too soon to be confident of anything but ....
It'll be interesting to see if DLM sees the lower error rate and takes off at least some of my 8ms interleaving (D: 1113).
Maybe cable routing, even for a 2m cable, is more significant than I thought.
Moved (with trepidation turned relief) to BT Infinity 2 for upload speed. Happy BE user for several years.