Steps to reproduce:
Mobile

Web:

I did a quick test and found that the local path was used in the block:
<!-- wp:video {"id":2} -->
<figure class="wp-block-video">
<video src="///data/user/0/org.wordpress.android.beta/cache/VID_20190722_113956.mp4" controls="controls" width="300" height="150"></video>
</figure>
<!-- /wp:video -->
I tried the same experiment with Aztec and the correct (remote) url was set in the video shortcode.
I wonder if this is linked to this one https://github.com/wordpress-mobile/WordPress-Android/issues/10203
I was able to upload a post with a video correctly once in Gutenberg. IMO this one needs some more investigation on the wpandroid side first.
This may also be related to https://github.com/wordpress-mobile/gutenberg-mobile/issues/1152
I've seen this issue before, but in testing this now I think the issue has been resolved. Tested both Android and iOS. If someone else can double-check that the issue is fixed, I think we can close this.
On a related note, I still see #1152 (video added on web shows invalid block on mobile) occurring.
Can confirm, (tested on WPAndroid only)
Actually I can reproduce from a Jetpack site.
Also, it looks like the issue can be resolved from the block editor "Resolve" function. It seems to be missing an empty value for controls (="") in the video element:
