Server Connection Issues

[Taurus]

We have the second round of our pak192.comic multiplayergame now running, but one of our players has big issue. Everytime he  tries to connect to the server, he crashes it with his loading time. Server is in Austria, he is in Italy. For all the other players it is working fine.
We are using ST 112.4 r6999 with the latest version of the pak192.comic. It is very likely to be his internet connection because he already had to leave round one because of the same issue. Does anyone know how to fix this? Switching providers is not really an option. He tried it with a different computer already.

[prissi]

Is the server dual stack enabled and he gets an IPv6 number and his provider prefers IPv6?

[Ramagani]

Ther server work with IPv4.