In MDL-79391 H5P interactive Video -  It is outlined that an interactive video can not be deleted or re-uploaded. This issue could not be replicated by anyone investigating the Bug and was therefore closed. 

In MDL-79707 Boost styles break H5P styles when scsspre and / or scss settings are used - It is correctly identified by Gareth that when arbitrary SCSS definitions are used, the h5p iframe is affected. Unfortunately, this ticket has been resolved as not a bug.

I have found that the MDL-79391 bug is caused by the issue raised in MDL-79707: the h5p iframe is being affected by Boost scss and scsspre settings. 

1. Set up an interactive video on h5p. Note that when you edit the interactive video it can be deleted or the video can be reuploaded
2. Make some benign and arbitrary non-related scss changes in the theme settings. For instance, I used fieldset#id_moodle_additional_names {display: none;}
3. Purge the cache, go back to the interactive video, and try to delete or re-upload the video. 
4. Note that alongside the broken css in the iframe, you can no longer change interactive videos.