Drag and drop states on submit for decoy objects with no defined drop target

I have created a drag and drop interaction with 3 drop targets and 6 drop items (3 correct, 3 decoys). All works well, and the feedback works as expected.

However, I can’t get the drop states to work the way I want. I want the drop state of all drop items to change – whether or not they have a defined drop target. What actually happens is that the drop state changes for items that have a defined drop target, but not for those with a drop target set to “(None)”.

(See the attached Storyline 2 file for a demo.)

So is there a way to achieve what I want using the standard SL2 features? If not, is there an alternative method? For example, is there a way, using a trigger, to test an drop item for correct/incorrect drop target?

Thanks!