HTML embedded videos sometimes display, sometimes don't

Pretty much as the title states - HTML embedded videos will sometimes display, but sometimes they just won’t. Occasionally they won’t even display in the Webflow designer preview, but it’s also happening after the site is published. To make things even more confusing, sometimes the videos that show are different to the ones that fail to load in the preview, and vice versa.

All files are uploaded with Dropbox and linked correctly. (read-only link attached)

Please help!