Noise margin has dropped to 8-8.3dB for the last few hours. Is that because it's off-peak, or because of the test socket? Or neither, i.e. is it normal for noise margin to change every so often?
If your noise margin has dropped, your speed should have increased.
It will be due to DLM seeing an improvement on your line possibly because the impairment is within your internal wiring which has now been disconnected.