Hi,
This is known limitation of this system the same way the physics constraint component will not work with a geometry collection
This is because the GetBodyInstance() method on a GeometrryCollectionComponent will return a null value
We are working on addressing those limitations, so stay tuned for future releases
I guess your best option in 5.0.3 would be to use fields to manipulate broken pieces of the geometry collection
Hope this helps
Cedric