[HeyLaughingBoy]

In the early days of consumer DSL, I had really, really bad service and I kept calling to complain and the phone company kept saying they found nothing wrong. Finally they must have gotten tired of me calling and they sent someone competent. He traced my phone cable all the way back to the box a couple blocks away then came back to tell me that he found the problem. One of the wires in the pair was not actually screwed down (or punched down, IDK): it was just touching the terminal. So some of the time it worked just fine, but I'm guessing that if a big truck or something drove by, the vibration separated the connection, and my DSL would go all to hell.

His guess was that (a) nobody bothered looking in the box and (b) they were just testing voice quality, which was fine, but the actual DSL signal was showing lots of dropouts.