Hi,
I am revisiting this post as I am back to my home location after being away for nearly 2 months. ok, so I have swapped the draytek 2860 for the PFsense box again (with the draytek 130 vdsl modem).
Again, draytek 2860 works fine, but pfsense has the same errors even with IPv6 disabled.
I will contact the ISP again to see if I can make them work