Rotation of non-Camera object not the same as the rotation viewed by the camera

I have a Camera attached to a Player object. It has a movement and a camera movement (looking around) script (and some more which don’t interact with the camera or the mentioned objects at all), as well as a CharacterController from unity and some 3D objects.

problem

My problem is that when I have a child to the camera and I give that child another child, which has a Sphere set 5 in front of the camera, and I rotate the camera, the sphere is not in the middle of the image shown by the camera. It is only in the middle of the camera (the middle being represented by a dot on the Canvas which is static) when the rotation is (in Euler) 0,90,180,270,360°.

I have tested a lot of different methods and checked the script if they change anything about it, but even when I had just a camera moving a sphere, it did not match up. The Camera also doesn’t have any settings that could result in the mentioned issue.

How do I fix this?

Any help or advice is greatly appreciated!