Thanks for writing in! Missing icons are very common, and it’s usually due to cache, or icon files are deleted, or blocked and it’s something any theme could do especially it’s dependent to those files.
In your case, the SVG files aren’t loading or not readable. Though, I can say the SVG file exist and accessible, it’s just that the builder is unable to process it. And since SVG are vector data, it could be affected by other features or encoding that will render it corrupted. As of now, I can’t fully find the details from the admin but this could be hosting related.
If you are hosted in SiteGround, you can turned off HTTPS Enforce within SiteGround panel. There might be a relation to this HTTPS setting in your case if you are using a different host. Please refer to this thread
Hope this helps.