I have a Martix Preview that is formatted as follows in the desktop version, however when I publish to to the web (and update the app) then the formatting is completely different, as can be seen in the 2nd picture. This issue only occured approx 2 days ago (ca 20/06/2017). Is this a known bug that is being worked on does anyone know?
According to your description above, I have tested it with the latest version(2.47.4766.801 64-bit (June 2017)) of Power BI Desktop on my environment, but was not able to reproduce the same issue.
Could you share a sample pbix file, so that we can help further investigate on this issue. You can upload it to OneDrive or Dropbox and post the link here. Do mask sensitive data before uploading.