Why can't it be crosstalk? If your line randomly dropped 2dB from 3.3dB to 1.3dB and resynced at a lower speed still at 3dB, then that sounds to me like a crosstalker.
edit: I'll clarify that a bit more. It's unlikely a new service was activated on Sunday, but it could well have been activated on Friday and they only just connected their modem. It's also very possible a crosstalker has been on holiday with their modem off (it is the holiday season) and returned on Sunday and turned their modem back on. Either way, a 2dB drop in snrm with a roughly 6Mb drop in sync matches crosstalk.
Looking again at the stats you posted I would guess a crosstalker was on holiday.
sync 72443 Kbps
Edited by j0hn83 (Mon 11-Sep-17 15:03:22)