Crazy bug that was driving me nuts:

I had a placeholder (hidden) iframe for a YouTube video with src="#".

The "#" was causing my layout to re-render within the iframe even though it was hidden and not displayed. This resulted in all of my assets getting loaded twice!

To fix this, all I needed to do was use src="" as the placeholder instead. I am not sure why this happens yet, but I will update this post once/if I find out.