The capping and loosing sync are completely unrelated as ADSL24 have no control over the exchange equipment, best thing to do is borrow some one elses modem/router and put it on the line with a known working filter in the test socket if that still doesnt work then its deffo a BT fault.
Have ADSL24 run any etsts on the line as that will tell in most cases if the problem is with your equipment...



