Have you tried using a different ADSL filter ? I had a similar problem recently which eventually (by trial and error) I identified as a duff filter (supplied by BT I may add) ... worth a try ?
Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
This poetic animation about monsters is illustrated in a Van Gogh painterly style
Apple predictions 2017
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.