This seems to be the effect of crosstalk on my connection:-
Sync speed was around 30Mb 27th December, had reduced to around 26Mb by 5th January & reduced again to not much over 23Mb 19th April.
Error seconds have now increased from around 100 or so per day to around 250 per day (sometimes exceeding 300) & CRC/HEC & FEC errors have all increased, showing bursts:-
I have eliminated any internal interference by running the modem from a car battery & grabbing the stats with a battery powered laptop whilst all the internal power was completely switched off at the incoming mains consumer unit.
I don't THINK this is a physical fault, as such, as my connection is otherwise very stable with very few disconnections & SNRM tends to hover pretty steadily around the target 6 dB.
I believe BT are currently trialling Vectoring which may improve crosstalk matters.
However, from what I have read, as my D-side bundle also includes other users' ADSL connections over 1000m or more, Vectoring will have quite a limited improvement as it only works with like for like VDSL2 services from the same DSLAM.
ADSL 'interference' will still apparently have quite an effect & will still require various levels of Interleaving & INP to ensure stability for VDSL2 connections.
Anyone else seen similar connection changes & does anyone know if the HG612 modem is 'ready' for Vectoring?
I have no idea when/if BT will be making Vectoring available/compulsory for all VDSL2 users - any idea, anyone?