I am attempting to embed the 3DContentCentral viewer on my site, which is built on and hosted by Shopify. I copied the embed code directly out of the model page and pasted it in, here:

Test page – Pulse Research Lab

For most of you, that page will operate properly. But for some browser/site combinations, it fails:

1. Safari/Mac fails, rendering the iframe as a blank box.
   1. But the problem is not with Safari itself, because I have pasted that exact same embed code onto a minimal page on my personal domain/server, and it works fine: http://www.kan.org/misc/link.html
   2. So it appears that something about Shopify is helping it fail.
      1. My brother hosts a different site on Shopify, and embedding the same code on his site fails identically, so the root cause is not my Shopify theme.
2. I tried making another test page with the embed code from a different model, and it behaves the exact same way as my first test page:
   1. Test Page 2 – Pulse Research Lab
3. All pages load properly on Chrome/Mac, Chrome/Win, FF/Mac, IE/Win, and FF/Win.
4. For all failing cases, if I inspect the failing iframe and open the src URL in another window in the same browser, it renders properly.

Shopify Support says they can't figure out the cause of the failure, and they don't see any errors.

Can anyone here debug the renderer and see how it's failing?