Iam running a Teamspeak Server. Since 2-3 Months 2 Members cant join this Teamspeak anymore. They can connect to others servers on the same Maschine and can connect to others Teamspeakservers in the World.
They tried with direct IP, with Domain, with and without Port (its the default one).

Domains are :

I have no SRV DNS Entry, so TSDNS should be used.
The only thing i could imagine is, that they are using DSLite, and thats somehow brakes Things... I have no IPv6 Adress.

Hope someone has an idea.