Line attenuation jump from 21db to 49db?

[#1]

Yesterday evening I had a more-or-less stable (up for 3 hours at least), albeit slow (2400 d/s) connection.  Line attenuation was reported as 21db, and noise margin was also about 21db (downstream).  Overnight the connection looks to have got very unstable again - with multiple drop-outs since about 3am.  I notice that line attenuation has jumped up to 49/24 (down/up) and noise margin is back in single figures (9db), connection speed is down to 2200 / 324(!).

I understood line attenuation to be related to the distance to the exchange, if so why can it more than double?

Has anyone else observed this?

[#2]

Hi there, 

An increase in SNR would happen as a reaction to increased noise on the line. That can happen due to an issue with the line or with equipment connected to it. 

I've been running line diagnostics and it has actually identified a line fault, I've added an update in relation to that the account for you https://www.plus.net/wizard/?p=view_question&id=171384495 

Adam