BSP disapears if I deform it

Hello to everybody.
Maybe I do a stupid mistake, but I can’t find the solution. If I deform 2 BSP meshes as you can see on the attachment and I move them to close,
the first one will disapear in dependence of the distance of the other mesh. How can I prevent this?

To create a 4 sided pyramid didn’t work with 4 deformed cubes, as you can see on the first announcement. So I had to solve it only with one cube wich I deformed
by splitting and deforming vertices.

As I also could see there is a Bug Report Nr. UE-15621 for the problem I have. Maybe some of you guys can give me a hint if something is fixed.