it is always possible the filtered faceplate is faulty and that can be eliminated by connecting to the test socket with a filter I am sure that CS will ask you to do the same
@Marc68 as shown on my diagram. Even the internal connections inside the filtered faceplate, can give problems.
Which one is it?
It's the one on the right. I've tried replacing the faceplate with old type filters, and the engineers have tried replacement filters too, so that has been ruled out. As far as the HR fault is concerned, the latest engineer did say he'd replaced the crimps in one place below the pavement, which were corroded. This seems to have helped a bit but not fixed the noise problem completely, so tracking it down is pretty difficult as you say. Pity there is not some sort of a sensor that can detect it from above ground. I did have a problem with moisture on the cable years ago, before I even had broadband, that caused a noisy phone line.
That`s fine. The Openreach Field Technicians do have testers that can detect a break or poor connection, but as its intermittent, it can only usually be cured by manually remaking each joint, as its not possible to look inside a crimped joint.