Jojo reset your target noise margin to 6dB on 20 Apr. From the information you posted on 21 Apr the target is still 6dB and that gave you a sync speed of 12217kbps - so that's about the best you will get. Resetting the target noise margin causes the DLM to forget all it knows about your line and start another 10 day training period to gather that information. That will run until 30 Apr.
I really think leaving the router alone - don't restart it - is the best thing to do. If the DLM wants to restart the router it will do so. "Helping" is likely to confuse things, and might well be detrimental.
Restarting the router through its web interface has the same effect as switching the router off, then on again. Preceding that by disconnecting from Plusnet is recommended to reduce the chance of the DLM taking the re-sync as a dropped connection. However please resist the urge to restart the router.
Plugging an extension cable into the master socket and connecting your router (via a filter) to that is not recommended. It might be OK, it might cause problems - impossible to say.
David
