3d settings lost when symbol linked to custom class

Flashplayer 10.
I have clip A in library containing clip B that has some 3D parameters applied to it (rotation etc).
I place clip A on stage and run movie. Nema problemas.
But. If I connect clip A to a custom class (clip B is a public property of that class), all the 3D settings of clip B is lost.

Does anyone know why and how to get around this?
Do I have to set all the same 3D parameters in code?

EDIT: Tried to set the container (clip A) to extend MovieClip instead of Sprite and it worked!? 3D parameters are intact.
If anyone understands why I’m interested to know.