I don't know if it's the browser (Chrome Version 67.0.3396.99 (Official Build) (64-bit)) or the upgraded SL360 but within the last month, I have noticed that the drag objects are either hidden or invisible when previewing and viewing in Chrome. IE works fine. Drag objects are visible.
Attached is a .story with three Drag and Drop pages. The last one works. It also does not have a colored shape behind the objects as the other two two questions do in the slide master. It's almost like the slide master BG is covering the drag objects.