It may be worth trying to connect o a different Teredo Server. Here is a list from another post on this forum:-
According to a site i found, there are a lot of “official” teredo servers.
6to4.ipv6.microsoft.com
pnrpv2.ipv6.microsoft.com
win10.ipv6.microsoft.com
win1710.ipv6.microsoft.com
win1711.ipv6.microsoft.com
win1807.ipv6.microsoft.com
win1901.ipv6.microsoft.com
win1910.ipv6.microsoft.com
www.ipv6.microsoft.com
xbox.ipv6.microsoft.com
xboxvnext.ipv6.microsoft.com
Suggest you try a ping test against these hosts and set to the one that returns the quickest response?
Then set that one to be used by running the following command in an Administrative Command Prompt:-
netsh interface teredo set state servername = Teredo host from the above list
Packet loss is always concerning though, especially a figure of 60%, so this may be network issue elsewhere in the route. Maybe carry out some further tests re this issue:- How to Fix Packet Loss – Packet Loss Test