Slow sync speed and intermittent connectivity.

Dropped connections and a fall in speed are related. In your telephone exchange there is a “Dynamic Line Management” (DLM) system which monitors the state of your connection. This system increases and decreases the speed dependant upon the stability of your connection. i.e. it gives you the fastest speed your line will handle without errors.
The dropped connections indicate line instability, so the DLM will be stepping down your speed in an attempt to stabilise your connection.
The most common cause of dropped connections is a poor or faulty ADSL filter, or equipment on the line which isn’t filtered, so first of all replace the filter(s). Once a stability problem is resolved, the DLM will increase the speed after 72 hours of unbroken connectivity.