I can confirm the same thing happened for us on several sites. This only seems to occur when ‘delete unregistered thumbnails’ is selected, and it removes the svg files from the server even though they still show in the media library (with no thumbnail). The original file URL path throws a 404 error and the files are no longer in the folder when checking via FTP.
I think the issue is that the .svg files aren’t recognized as a ‘required’ thumbnail size, and hence being deleted rather than ignored (which is what should be happening with SVG media).
