Configuration of Dragula javascript component

I created a e-learning activity that emulates a dominoes game. I used the Dragula javascript component to make the tiles draggable etc. The game functions like this: the user catch the tiles and put them in the drop area. After this, he should rearrange the tiles in a specific way that makes sense with the context of the activity. My problem, however, is that the tiles don't remain draggable after they are put in the drop area. You can see the game here: [login to view URL] Please, contact me if you are able to solve this problem.