Steps to reproduce:

1. Create a new 'drag and drop onto image' question.
2. Add a Question name/text and upload a background image.
3. In draggable item 1, choose an image file and check JS console, you will see "Uncaught TypeError: Cannot read property 'simulate' of null"
4. Add text for draggable item 1
5. Check drop zones and "Draggable item" will be empty.

Workaround is to save page and edit question again. This time the "Draggable item" will show text for image.