I came across this post and decided to check its revision (to explore the source code for the YouTube video).
If we choose a view then refresh, then the views show up correctly, except for the side-by-side view:
If we start with markdown view, then switch to inline view, the view is missing the change which comes after the video (please refer to the side-by-side view above):
If we switch over to side-by-side view, it is empty:
This bug also cause an extra copy of the inline view to be appended whenever we switch between side-by-side view, then back to inline.