Got myself a new filter today and have plugged to the new socket. I see even the backplate was changed, wonder if it's some dodgy wiring to the terminals? Anyhow, rebooting hasn't helped, SNR now up to 9db.
Connection Speed (Kbps) 39994 7200
Line Attenuation (dB) DS1:14.1 DS2:33.7 DS3:52.6 US0:2.5 US1:25.2 US2:41.4
Noise Margin (dB) DS1:9.7 DS2:9.6 DS3:9.7 US0:10.0 US1:8.4 US2:6.8
Figures before the fix were:
Connection Speed (Kbps) 52112 10099
Line Attenuation (dB) DS1:14.2 DS2:33.9 DS3:52.8 US0:2.5 US1:25.5 US2:41.6
Noise Margin (dB) DS1:5.3 DS2:5.1 DS3:5.1 US0:6.0 US1:5.3 US2:6.0
Can't pretend to understand what they all mean, but I know some of them aren't good

Struggling to get any sense out of Sky now.