Archviz Scene - background curiosum

Hey everybody,

does anybody know what is going on here?
I am using 4.22.3 UE.
Initially the scene was setup with an editorskysphere with HDRI, a skylight with HDRI cubemap, a directional light for sun.
After several bakes but weired reflections on the materials I started wondering what the problem is.

I turned off, and delted everything and without anything light related this HDRI is still visible in the background but it is “a bit” rotated.

Any help? Thank you so much! .

Best regards.