Turn off the new noise source!
I'm not sure what/where any new noise source could be. Nothing has changed at my end - I'm using a Vigor 2860n+ router with recent firmware, in the master socket with an ADSLNation faceplate, and no extension wiring attached. That is on a UPS (we get occasional power cuts/brownouts), so is well filtered from any mains noise.
No new electrical/electronic equipment, and the nearest neighbour is >200metres away. The phone wire runs underground in a straight line to the exchange and probably doesn't pass within 30 metres of any property along the way (and there aren't many of those).
There is no audible noise on the line, and no new notches in the tone graphs.
There is the one (1) upload FEC error today, but no other indication of any interference/noise apart from the drop in SNR.
Since the profile is at the maximum, and there doesn't appear to be a separate upload profile, is the upload likely to reset at some point?