3D Objects used in Drag and Drop

I don't have a particular solution for you, but I'll share my thoughts although I'm not certain about what you're expecting.

If you are referring to the drop items not always returning to their start location when dropped outside of the correct target, then consider adjusting the drop behavior in the Question Tools | Design | Drag & Drop Options dialog (first section). Change 'any drop target' to 'a correct drop target' to allow auto-returning while still over the larger group drop zones. 

If you mean why don't the drop item states always return to Normal when they return to their starting positions, that's because the auto-return process doesn't activate any triggers. Events like ending intersections, ending mouse hovers, losing focus, and the like don't register when the return happens, so the state remains as it was. This is most evident when your drop items haven't yet exited the Drag Over states trigger by intersecting the larger group drop zones. I don't have a good solution for this other than not using drag item state changes during the drag operation, or perhaps only triggering the state change when the drag item is over the specific correct target, rather than the entire group drop zone.

On another note, you might consider setting the interaction to snap dropped items to the center of the drop targets to better align your tools with the shape outlines (as in the previous demo slide). This option uses the shape from the initial Normal state as a center reference however. Your other states would need to be manually adjusted to align their centers with the center of the Normal state.