Video elements are showing up like this in the Designer in Chrome (MacOSX v67.0):
It is the same when viewing the published site but when I hover on the video element I get this:
The published site works perfectly fine on Firefox (MacOSX v61.0.1):
and on Safari (MacOSX v9.1.3):
Clearing Chrome’s browsing data made no difference.
Any ideas why this would be happening?