I can successfully add gifs to an Image webpart on a SharePoint modern page. This works well.
What I would also like to do is add a gif to the thumbnail within a SharePoint news articles page properties. There is an option to add a thumbnail, so I'm selecting a gif using this option. I've used both approaches, first to upload the gif directly when clicking on upload in the SharePoint media selector, and second approach to upload the gif to the site first and then select from the SharePoint media selector. Neither options changes the results.
The results are that sometimes the thumbnails load as gifs which is great because within a News Webpart the gifs are animated to make the page feel more engaging. However sometimes the thumbnails load as png files and are static.
Now here's one thing I've noticed, when it loads successfully as a gif and I inspect using developer tools, I can see the src is the gif file in the siteassets folder. When the same thumbnail doesn't load successfully and I inspect using developer tools, I can see the src has switched to 'blob:https://[tenant].sharepoint.com/90b28b2c-0993-40ae-9f51-ecca0817fb3d'. It looks like it's auto generating a .png file.
Is anyone else seeing this odd behaviour??