Mesh (a part) not casting shadow

I recorded this small video because I can't understand why a part of my mesh does not cast shadows.

https://s2.gifyu.com/images/Sumerian-Console---Google-Chrome-2019-04-03-15-22-46.gif

As you can see a part of the mesh (the vertical one) cast shadows correctly, another part (the horizontal one) doesn't. I tried to invert the horizontal part's normals, but nothing has changed.

Can you suggest me a way to solve this problem? Also by using other tools (e.g. Blender) if necessary.