saguaros sorry for the long delay of my reply. In the meantime I tested it with different versions of XAMPP. Here are the versions I used for the test (where the version numbers refer to the PHP version, but you probably know that).
- xampp-windows-x64-7.4.30-1-VC15-installer
- xampp-windows-x64-8.0.23-0-VS16-installer
- xampp-windows-x64-8.0.25-0-VS16-installer
Unfortunately I didn't find a XAMPP version using PHP version 8.0.24, since that is currently used by my hosting provider. And there News Show Pro GK5 works fine.
What I noticed is that with XAMPP News Show Pro GK5 worked with the PHP 7.4.30 version but not the two 8.0.xx versions. Since it works on my server with a 8.0.xx version my guess is that it's either a PHP or another setting within XAMPP causing the problem. So far I haven't figured what it might be.