I just realised something I should have checked all the way back at the start of this, but didn’t think to check because the landline had just been repaired.
The phone is humming on a quiet line test. It’s not noisy enough to interfere with calls, but it’s not silent either.
It’s an old phone temporarily plugged into the master socket, not a dect by the way.
Fault reported….again.
I’m guessing it could well be why DLM hasn’t done anything to increase speeds.
Indeed it could well be.
Possibly an earth contact fault causing the hum.