No GI/Lightmass bounce on geometry placed by blueprint actor?

Hi,

I built an environment (simple room with windows) in maya, imported the geometry and put it into a blueprint actor.
I placed the actor within a level and set one directional light - lightmass is turned on correctly and the lighting is built (ignore the light leaks!):

Somehow I only get direct lighting - no bounces on any of the walls or the roof.

When I import the parts of the environment directly to the level, it works:

Can anyone tell me why geometry, that is placed within a bluepinrt actor, does not react the same way as
directly placed geometry?

And how can I solve this? - as I want to build the environment as an actor for reuse in other levels.

Thanks!

Make sure the mesh’s mobility is set as Static in the blueprint.

Yes, make sure it’s not movable.

Thanks! That solved the issue!!

But now the problem ist that the light build process takes ages with the blueprint actor but only seconds
with the directly placed geometry.

Is there maybe something else I need to pay attention to?