Unfortunately none of the posts include "imeta" tag, which is useful for calculating the aspect ratio and potentially a thumbnail of the videos you publish.
For user's on Nostria that doesn't have auto play for all videos enabled (default off, it will auto-play short form videos), it renders like this now. I will improve this so it starts loading the videos, but even then, the UI will jump a bit while it downloads parts of the video to render a preview and discover the movie aspect ratio.