Although this thread is old maybe you can also help me. I have exactly the same problem as david00 and have done the testing using the test socket.
Incoming calls are not affected and my fibre broadband works fine (76Mbps) even when I am having the dial out problem
I am getting nowhere with BT as although I eventually managed to get it logged as a fault, despite a normal line test showing no problem, on my account it shows fault ongoing and expected to be fixed 3 days ago. I have had no contact from BT since logging the fault last Monday and if I try phoning for an update they start the whole process again doing a normal line test.
I originally posted this problem about 10 days ago and it was suggested that
"there are possibly two areas of suspicion , the exchange line card, or the broadband port your line uses (even if the broadband performance isn't affected)..these issues won't show up on a 'line test' "
Please help if you can
You already have an active thread about this here.
Please can you update that one, and not post on an exising thread.