Shadows in EEVEE disappearing in final render


I am trying to get into EEVEE. Therefor I set up a quick scene to get the hang of the lighting. Unfortunately I get strange results in one part of the render: the wall.

In the preview it is more like expected:

Here is a link to the .blend file:

I tried toying around with shadows/contact shadows, area lamp settings, irradiance volume and reflection plane. Nothing had any influence on the final render so far. Any hint is really appreciated, thank you.

The Normals on your diamonds need to be flipped but that didn’t fix it yet.

If you delete everything except Area, Camera, Cube, and Plane.001…
And you flip the normals on the diamonds…
It renders like the preview. (I added the magenta to see if that face was rendering)
diamond shadow

EDIT: The normals don’t even seem to matter.
diamond walls
daimond normals