Just a quick update to say an engineer is visiting tomorrow morning.
OK, that's a start.
Make sure they perform a 'PQ' test (pair quality).
Make sure they ensure that any other points connected on this line are disconnected by removing the faceplate from the NTE where the VDSL modem is fed.
If they have used a data extension kit, ensure they test at either end to show no loss in sync rate.
Please ask that they use the manual VDSL test rather than scripted tests on their JDSU/Exfo, the scripted ones have a sneaky habit of masking errors.
Remind them, politely, that if they ring for a reset
before they do their faulting, they will possibly mask the cause. They should be looking for low downstream, possibly varying, snr.
Good luck, let us know how you get on, who knows, if you are Reading way, it might be me !