Blog in Azure: IPv6 fail on some users

This is what I got from an IPv6-user:

The TLS-handshake succeeds, but after that everything breaks loose. TCP-packets are out-of-order, there are retransmissions. The above packet capture starts at second 23 and there is a failing retransmission at second 53, so obviously there is not much of a service from my website.

There are perfectly working IPv6-users, I have requests from 14 separate IPv6-addresses in log, so it works perfectly for somebody. Ultimately I have no idea what's going on, or how to fix it. If you know, drop me a comment.