SNR Reset process - how does it work?

[#1]

I believe high error rates can also trigger an increment in the target SNR - but yes drops are more usual.

[#2]

I had that problem a year ago when Plusnet reset 3dB as the DLM kept put my line up to 9dB and logged a fault team. The fault supplier spoken to bt on echat and managed to turn off DLM and fixed snr 3dB. I had disconnected the router many times over the last 6 months and DLM haven't rise my snr. It's all stay at 3dB for the last 10 months now. Even I did mess around with new BT Openreach modem, BT Home Hub 5 and Netgear DGND3700v2 and the DLM haven't kicked SNR rise ever since. It stayed at 3dB.Thanks to BT for magic work around at the exchange.

[#3]

With an attenuation of 14dB at a SNRM of 6dB you should see a synch speed around 22Mbps.
The fact that you are way off this points to a line problem somewhere.  Have you done a quiet line test? 17070 option 2
Have PN done a line test (is your phone service with PN)?
If there is a line fault, SNRM resets will deliver nothing - as noted elsewhere, keep an eye on error rates... Indeed install RouterStats and get some constant monitoring reports 24x7 to see if there is a marked drift of SNRM / error rates.

[#4]

The main problem here is that the SNR Reset did nothing. In order to do a training, it HAS to try the lower target SNR's otherwise, it cannot check stability. The only excuse would be if the line was unstable or with high error rates at 9db. It isn't
During the whole process of TWO attempts to reset SNR, the level DID NOT CHANGE - not even immediately after the reset, which is what would be expected.