Thanks for taking a look at this. The reason I posted this yesterday was to ask about a different issue than the one that we happened to catch, and that is a slowly decreasing SNRM DS. What seems to happen is that after a retrain I get around 6DB as I should but then over a period of days if not weeks, that value slowly drops until it reaches 1 or 2 and then I get a resync which puts it back to 6 and it starts again. I just wondered if a bad line is something that could genuinely cause this, or whether it was an issue with the way the stats are generated from the router. Given that from an end-user perspective nothing changes, with the line remaining stable and the speed steady, it just seems slightly odd to have this slow erosion.
With regard to yesterday, I've never been aware of having a catastrophic event like that before, but then I haven't been monitoring it closely up until I got my Pi set up, so it could have happened before. However, I'm not aware of any DLM action over the past six months or so. In fact, the last time was when BT "upgraded" us Infinity 1 users to 76Mb and I had a full DLM reset. At the time I had been stuck on a banded profile and that caused it to sync higher at around 47. After 10 days of stable running it dropped to what it is now, about 41Mb/s.
I don't think my line is in a very good state generally. I'm around 300 yards from the cab but an engineer told me over 100 yards is aluminium, which is not good. Way back when FTTC came to my area and I was one of the first in the cab, I was getting mid-50s but crosstalk has had an impact, the last time about a year ago when my next door neighbour changed from Virgin to Sky and I took a 5Mb hit as a result. The annoying thing is my guaranteed download speed is 40Mb/s and I get 41, so BT won't send an engineer out. I don't think my line is ever going to improve even with Gfast so I may have to switch to Virgin, but they have their own set of problems (not least of which an over-subscription issue in my areas that took 2 YEARS to fix...). I'm just hoping my line gets worse - then I may be in with a shot of an engineer visit.