SampleAnimation animates only 1 sub-object

Hello everyone,
I am trying to figure out a simple problem.
I am trying to create a tool to extract images from a 3D model to create spritesheets.
Problem is that when using both:

animationClip.SampleAnimation( animationObject, animationTime );

or

AnimationMode.BeginSampling();
AnimationMode.SampleAnimationClip( animationObject, animationClip, animationTime );
AnimationMode.EndSampling();

it only animates 1 sub-object of the mesh!
The mesh is composed by an orc with a club.
Only the club is animated!
If I preview the animation in a custom window, with the same methods, it works correcty.

What possibly I am doing wrong ?
Thank you!