Drag and Drop: How to arrange dragged objects in rows without overlapping in a quiz?

Hi everyone! 

I've seen a template created by Nicole where the drag and drop quiz neatly arranges multiple objects into the target drop areas. Each object is visible and organized in rows that can be rearranged (see Fig 1). However, when I try to create my own version of the quiz, all objects I drag into the target areas end up stacked on top of each other at the midpoint (see Fig 2).

Has anyone encountered this issue before? I would greatly appreciate any advice or if someone could share a template that resolves this stacking problem. Thank you in advance for your help!

Fig 1. Neat layout

Fig 2. Stacking objects