Yeah everytime its been reset previously, it slowly deteriorates and the connection gets worse over time.
many connection benefit from running with 3db but some others like yours find that it is to low and it increases the errors resulting in slow throughput
I would contact mods and ask for the noise margin to be reset to 9db as john46 suggested and this should help reduce the errors and improve download. remember the increase in noise margin will reduce your connection speed
Yeah I've messaged then, i'd rather have a stable connection and sacrifice a bit of speed. This problem has been going on for nearly a year.