A few weeks ago I migrated to FTTC. It worked fine for the first couple of weeks, but since then I have suffered from frequent drop-outs. The tbb monitor will typically show 100% packet loss for a few minutes, then service resumes, to be interrupted again a few minutes later - rinse and repeat for several hours.
Sometime I also get longer lasting outages - a big block of red on the tbb monitor for a few hours.
My ISP have referred it to BT Wholesale, who have sent assorted engineers out, but without much improvement.
I have a router-to-router VPN to another ADSL (from the same ISP) site. The VPN is used for the other site to access a NAS on my LAN. I noticed yesterday a correlation between activity on the site at the other end of the VPN and the dropouts I got yesterday.
Is it possible that activity on the VPN could be pulling down the VDSL line? It seems unlikely to me, but I don't know enough about how these things work.