"decoding error" while Client request on MACOS

[DragisBlade]

I am new to GitHub and I hope that I do this here is correct?
I currently tracking down a very strange issue with HTTPS-Client requests on MACOS.

I am using Warp and Hyper-Client to create a Webserver and another Backend-Application calling that Webservers interface.
Actually, everything works well, on windows, and linux, even on macos.

But as soon as I execute a HTTPS-Call from within my application running on MacOS to any other Operating System it failes with the error error trying to connect: decoding error
The Error looks quite similar to this one here

Noticeable Things so far:

• If I use localhost to connect to my application running on the same Mac it works well!
• If I use <local-ip> instead, I get the error.
• No matter what I do, adding Root Cert to the HTTPSHandler, to MACOS or disableing all cert checks (danger_accept_invalid_hostnames(true).danger.accept_invalid_certs(true)) the error remains.
• Calls from Safari and Chrome on the same MacOS as well as other devices to my Application working well and are secured (Certificates are valid (even in MacOS))
• A Call with the same client configuration to some public web page, like https://google.de works well. Also local Webservers with HTTP (without S) can be called without any problem.

I would be very grateful for any thought or idea how to proceed ... in hope that I did not discover a hidden but somewhere inside some library...

thanks in advance!