A question on Max Attainable rates

Recently I had a lot of errors and my profile was banded to a very low rate less than 50% of normal. I decided to have installed a SSFP and move the master to exclude home wiring from the equation, and the engineer found no line problem.

I've requested the banding be removed. However, something noticed in the duration of the problem interests me. Normally the max attainable seems to fluctuate +/- ~10%, but what causes the greater one as in the following list, where line banding has been constantly ~3070 kbps?

12-Feb Downstream rate 8352 Kbps
13-Feb Downstream rate 7924 Kbps
14-Feb Downstream rate 8512 Kbps
15-Feb Downstream rate 6644 Kbps
16-Feb Downstream rate 6288 Kbps
17-Feb Downstream rate 6296 Kbps
18-Feb Downstream rate 6684 Kbps
19-Feb Downstream rate 6680 Kbps
20-Feb Downstream rate 6624 Kbps
21-Feb Downstream rate 6588 Kbps
22-Feb Downstream rate 8304 Kbps
23-Feb Downstream rate 5692 Kbps
24-Feb Downstream rate 8384 Kbps

Variations in the noise environment, which if you have wiring that was impacting i.e. picking up spurious RF without lots of kit recording 24/7 and time spent analysing likely candidates for the RF source impossible to say.

I must have misunderstood, thinking the max attainable is what the line from exchange to house was capable of on the BT side; also thinking faceplate would exclude domestic wiring.

Sorry!

And as the noise environment varies so does the max attainable