Drag & Drop not working in HTML5 output - Storyline 2

I am working within Storyline 2 and have built a freeform drag & drop interaction. It works perfectly within the LMS (Litmos) on a desktop, but when attempting to test on my iPhone, one of the final drag and drop items is not "draggable." 

The item that I can't seem to grab was formerly a line, so I imported it into Photoshop and expanded the canvas around it to be 100 px transparent, so it should be large enough for a finger to grab on a touchscreen (other objects that DO work are smaller than 100 px). I double and triple checked and my triggers, drag and drop interaction, etc. have all been updated to the new image. But I just can't seem to grab it still. I had read an article about drag and drop not functioning if you set items on a slide to "transparent" so I changed any objects that applied to and no dice.

I've been troubleshooting this for several days and need to move on with my testing. Can someone please help me figure out what I'm doing wrong? I'll attach the single slide below to remove any proprietary info.