[Bug?] Change mobility of SM actor detaches SM sub-component

There is a static mesh actor Door with another SM sub-component. Root component is the doorframe, and the subcomponent is the inside of the door. Both are static. When I place the actor in the level an put it’s mobility to movable the sub-components get detached and moves to 0. It seems the change of mobility of sub-component occurs after the attachment. I doesn’t happens if the Actor is just a normal actor, not SM Actor.

I would like to know if this is intended behavior or a bug and if there is a workaround.

Video illustrating the problem: 2019 03 12 16 52 51 - YouTube