I have a similar problem. When I do the BTW test about half the time the download speed is 0 Mb/s, but when BT test it from their end it is always solid at around 24 Mb/s. My computer is connected to the BT Hub via a LAN. I get the same results with both the hub 5 and the 6. In practice this does not affect the computer, but I cannot connect the TV to the Internet via WiFi to the Smart TV or my I/N enabled BlueRay player, which worked well for at least 2 years. A message comes up " connection is inconsistent". I have raised this issue many times with BT tech. support with always the same response.
If you like a post, or want to say thanks for a helpful answer, please click on the Ratings 'Thumbs up' on left hand side. If someone answers your question correctly please let other members know by clicking on ’Mark as Accepted Solution’.