Why does shoutcast resolve the Dynamic DNS as a redirect?

[Tormy]

I wanted to use a DyDNS system, to avoid that a change of the IP address of the server, could cause the off of Shoutcast ...
We are in 2019 and "manual staff" are belonging to past century

thus I setup a Dynamic DNS on a free service just to test. It works fine.
But Shoutcast, resolves into the IP address of the server, as a redirect 301

I give to it: http://<myradio>.dynu.net:8000
and after a hile, he turns into http://<myip>:8000

I no want this at all
What can I do? Any settings into the .conf file?

[Tormy]

No one knows? Or no one got the same issue?

[NJK]

[Tormy]

just to complete the information, I use dynu DNS