I faced different Occlusion behaviour for 5th and 4.2d Babylon versions.
Just try it Babylon.js Playground on 5 and 4.2 versions and you will see.
It seems to be broken.
We can also see in the demos of the documentation that the sphere ooculted/disappeared no longer displays when it should be when the camera can see it. (work with version 4.2)
Having a look.
Will be fixed by:
Thank you for such a quick reply and solution)