What could have happened to my upstream

[#1]

This is an odd one to which I have no clue  how or why it has happened
After months of a rock solid connection with the upstream at 888kbps noise margin about 10 - 10.5dB yesterday at about 17.00 the upstream noise margin dipped suddenly then recovered to about 8.5dB
This morning I found that at about 04.28 it had resynced with these stats
xDSL linestate up (ITU-T G.992.3; downstream: 3696 kbit/s, upstream: 672 kbit/s; output Power Down: 18.8 dBm, Up: 12.6 dBm; line Attenuation Down: 49.5 dB, Up: 26.4 dB; snr Margin Down: 6.2 dB, Up: 6.0 dB
So there was obviously something wrong with the upstream although the noise margin had increased to nearly 13dB when I switched the computer on
One manual resync later
xDSL linestate up (ITU-T G.992.3; downstream: 3927 kbit/s, upstream: 888 kbit/s; output Power Down: 19.3 dBm, Up: 12.6 dBm; line Attenuation Down: 49.5 dB, Up: 26.4 dB; snr Margin Down: 6.2 dB, Up: 8.3 dB
The upstream noise margin has subsequently increased to about 9.3dB after two incoming phone calls
This is the graph of upstream noise margin

[#2]

Jim,
That sounds like (sorry for the pun) line noise, not unlike the long running Jem16 thread... 
Kevin

[#3]

An alternative - but I have no idea if it is even possible - is that BT Openreach were messing about in the cab as they are in the process of setting up a fibre cab next to it although I haven't seen any activity for a few weeks. Of course I only go past it about twice a week so that doesn't prove anything

[#4]

BT working on a late Saturday morning - what you been smoking Jim?  

[#5]

Good point - I hadn't thought of that - silly me 

[#6]

BT regularly work Sat overtime round here.
-Probably because there are so many never ending faults - they are in the local cab probably once every two weeks, and that's just when I see them!

[#7]

Morning Jim
I was having similar problems recently.
I was having problems with packet loss during peak times, submitted a ticket and I had interleaving turned on, which I requested be turned off again.
Wow what a weekend though, last night was something else. See my tbb graph 😮
Doing a quite line test sounded very static and my SNR on my upstream was something like 14.4.
Seems something happened early this morning to drop my ping back down, will let you know if my SNR and line noise is gone too.
Considering winning the lottery and just getting a leased line Sounds so easy, right ?