You are in the bottom banded profile due to all the disconnections and or resets. If you could maintain a stable connection then banding will release with noise margin reducing in stages down to 6db with speed increasing at each stage
I've reset the hub to default tonight. No other resets (eg by the button) were done tonight, or last night. If it's getting reset multiple times, it's not by direct action.
OK, done the quiet line test, used the test socket and diconnected everything except the phone. Listened for a while (quiet line test message was repeated 4-5 times). There is a barely discernable backround hum, and an occasional very faint click. There doesn't seem to be a discernable pattern to the clicks (time between clicks seems random).
It sounds like you have a line fault which is causing your broadband to disconnect which is in turn causing DLM to take action and slow down your connection. Report the fault as a noisy line rather than a broadband fault. Once the fault is cleared your speed will improve.