Hi, I found some problem when booleaned mesh is imported to RC.
Here is the mesh in Blender.
and this is in RC.
the shape of booled mesh changed! What’s wrong with it?
and this is in RC.
the shape of booled mesh changed! What’s wrong with it?
Couple of links for you to explore that can explain better than I can 
Your issue is non-manifold edges which are “edges that connect more than two faces in a mesh. They create an ambiguous geometry that cannot exist in the real world, and confuse the software about the inside and outside of the model.”
How to Fix Non-Manifold Edges in CAD Software.
The boolean operation could be dropped and replaced with a different technique which might solve your issue https://www.youtube.com/watch?v=ZrQIq6pCtPE