Hi,

It's not a bug - because the excerpt from WordPress will auto remove all the shortcodes inside the excerpt - and your video running inside posts page appears by a shortcode from WordPress.

I have an easier way to make it work fine - use video post format.

Please edit the posts and select video post format & put the video URL to "Video Data"

Check this image.

And the video will auto display - you don't need to put video URL inside your content anymore.

Best Regards,

PenciDesign