Using Grav installation twice

I have a (linux) server which runs multiple web servers using different host names.
So I have installed Grav in a folder of the server under the hostname gravprod1. … and there it works well. Now I decided to roll it out and to set the root folder of the web server with the host name “www” to the same folder of the server.
But that does not work. Looking at pages delivered from the www web server I see only fragments of typical Grav HTML but not a full page. (The pages on the gravprod1 web server still work ok.)

Is a Grav installation linked by something to the hostname of the web server? And if: what needs to be changed.
Does the cache needs to be reset? (Tried, didn’t help) Or something else?

All you should need is the cache to be cleared.

After clearing the cache it took some time but then the site content was delivered properly.
But the administration user interface still (= 6 hours later) delivers only HTML fragements.

Sounds like some aggressive caching on your web host?