@jid: I don't know if this helps, but I had a line drop at a similar time (just after midnight on the 5th).
Before, my connection was a steady 5-8 - 6.3 SNRM (both up and down) depending on the time of day.
After the resync my upstream SNRM dropped to 4.8 - which I liked, since I got a couple of Mbps extra upstream! Unlike your connection however, it's remained "odd" ever since.
Currently, my line is showing 7.3 down/4.8 up - which is weird! (Some kind of banded profile)?
Looking at MDWS I see a lot of lines with lower SNRM than normal.
But since you mentioned vectoring, does anyone know what stats to check for if vectoring was enabled on an HG612?