Adding a video as background for Cover block sometimes results in "Problem displaying block"

[illusaen]

Describe the bug
Adding a video to the Cover block, previewing the post, and then cancelling sometimes results in "Problem displaying block".

To Reproduce
Steps to reproduce the behavior:

1. Add Cover block
2. Add a video to Cover
3. Click on "More > Preview"
4. Close Preview
5. See that Cover block shows "Problem displaying block".

Expected behavior
Cover block with video as background should be shown.

Screenshots
https://user-images.githubusercontent.com/13263478/113218145-a8103d00-9244-11eb-82b8-7cf8e540fbe4.MP4

Smartphone (please complete the following information):

• iPhone
• WPiOS 17.0 build 44694

Additional context
I was unable to reproduce this on my iPhone 12 Mini, running iOS 14.4 and WPiOS 17.0 build 44694 but @iamthomasbishop was able to reproduce consistently on his phone. Not sure what the difference is.

[dcalhoun]

This may be related to or duplicative of WordPress/gutenberg#28972. I'm not sure. The ability to recreate the issue may also be related to whether the site is simple, free/paid, Atomic, or self-hosted.

[illusaen]

This may be related to or duplicative of WordPress/gutenberg#28972. I'm not sure. The ability to recreate the issue may also be related to whether the site is simple, free/paid, Atomic, or self-hosted.

Thanks for the additional context! They do look related.