This is something to do with your servers
pagespeed mod. Look at the URL as you have embedded it in webp format:
xRotato,P20Snapshot.png.pagespeed.ic.2EKMaQaiiq.webp
The original file in PNG format that you uploaded however, is deleted by X3:
Rotato%20Snapshot.png?uncache
Basically, the file is deleted. The only reason it's still on your page, is because you have EMBEDDED a pagemod-cached cached version. And to complicate matters, it looks like you have copied the url of the image that showed up in your browser earlier, which was modified by your servers pagemod, resulting in a file converted to webp format.
Why not just remove the EMBED from your custom content? The image is definitely deleted, as you can see in the X3 gallery. Even if the pagemod webp version remains in your server cache (for reasons outside of X3's control), you should never embed images that don't exist as you clearly don't want them to display. Even if the image did get deleted (by pagemod), the embed would remain, displaying a broken image.