mark_t wrote: when I use the Openreach modem, the line usually 'resets' every 14 days or so.

Yes I think that is the DLM in action doing what it is supposed to, making periodic adjustments to account for line conditions. The reset period seems to be a function of how variable the line quality is, the worse the variation the more often it resets. On a line with virtually no errors it should never reset at all. But it should not do it any more than once per day (I think).

Found a useful article on it that clears up some of the questions: https://community.plus.net/t5/Library/FTTC-DLM-What-it-is-How-it-works/ba-p/1322799