My line #4 is going on and off constantly, losing sync all the time. Started yesterday at around 18:00. Has been reported to ISP, A&A, who are waiting for Openreach to come back to them with an engineer appointment date.
Meanwhile line #3 is a bit slow due to hollow curve malaise, that is: a misshapen SNR-vs-tones graph where there is a depression or hollow where the highest point of the curve should be. It’s down at downstream sync rate of ~2400kbps whereas it should be around 2900-3100 kbps compared to its previous state and compared to lines 1 and 2.
I think it’s very suspicious that line #4 failed when the thaw here began. Everything has been frozen solid here for week or so, and we have no water as there is ice in the pipes. Even though the thaw started seriously on Saturday it’s taking a long time for the warmth to reach certain parts of the plumbing system. What if water had got into a connection somewhere, then had frozen solid, and on Sunday it finally turned into liquid water again. The speed of line #4 downstream has been an all time record.
These are the sync rates before things went bad this weekend, and before line #3 went really bad (although line #3’s hollow curve phenomenon was evident already at that time and was responsible for line #3’s lower speed compared to lines #1 and #2)
Live sync rates:
#1: down 3165 kbps, up 531 kbps
#2: down 3154 kbps, up 586 kbps
#3: down 2869 kbps, up 409 kbps
#4: down 3392 kbps, up 582 kbps
That high sync rate was unheard of, scarily fast, and the link was completely stable, holding up at 3dB target SNRM for a couple of months (very roughly).