A few weeks ago I've noticed our internet has slowed down.  Did not take much notice as it was peak time, but the next day it was still slow.  Turned out the sync rate dropped from almost 9Mbps (where it had been for years) to 1.5Mbps.  Downstream noise margin was also around 40dB instead of 12dB.  Reboot modem and all back to normal.  Five days later the same thing happened, this time I just unplug the phone line for a few seconds and upon resync all was back to normal.  A few days later similar issue but all stats including noise margin are normal except for sync rate is just over 3Mbps, sometimes 2.5Mbps, and noise margin is jumpy (sometimes close to 0dB).

Tried the usual including a new power supply, no difference.  House is 2 years old, new wiring to the pole (then overhead to cross the road).  A couple of months ago kids damaged the main cable coming down the side of the pole (on the other side of the road), Chorus spent a few hours splicing and sealing, still looks fine.  All that is remaining is to try a different modem (which I might do sometime today) before doing a help desk support call.  Last night our smartest phone reported an unstable internet connection.  Any suggestions?  I'm using an SRP527W, been very good for a few years.