DLM confused into submission?

[#1]

About nine months ago my target SNRM went from its usual 6dB up to 9dB, for no apparent reason, and has resolutely refused to come down again. I've tried long periods of high sync, low sync, all to no avail.
On Saturday, I had a friend's laptop and router at home, investigating his wireless problem. I replaced my 2Wire 2700HGV with his Thomson TG585v8, but for some reason couldn't access the stats page.
Instead of putting the 2700 back, I thought I'd give my old Thomson ST585v6 an airing, and whadd'ya know - it synced up with a 6dB margin. Still OK this morning.
Coincidence? Or was the DSLAM 'woken up' by seeing three different routers within half an hour? 

[#2]

I had the opposite problem.  I spent quite a few years on 6dB with a 585v6.  I switched briefly to a 2-wire 2700hg and my target SNR margin went up to 9dB, never to come down automagically again
-- gyre --