I'd like some feedback from any telephony engineers on here as to what might be happening to my line. When the telephone line is active the downstream noise margin and max data rate nose dive. This doesn't happen all of the time so can be a bit of a pain when booking engineers. I have however captured it on video, you 'll need to increase the settings on youtube to make it readable.
https://www.youtube.com/watch?v=O-OMNvw_iew