Why are markers in Articulate 360 showing transparent on layers?

I have a similar problem. I created a drag and drop activity and included markers to give learners hints & additional information. The maerker's label text is overlapping with the drag item. Although I gave the marker label a white fill (no transparency), the drag item shows through as if the label was transparent. Why does the marker not go over the other items? 
All elements are on the same layer.