We've seen this issue reported sporadically but have yet to reliably reproduce it in order fix it. If you can provide precise steps to consistently cause the issue, please share them with us.
You can use the Recapture Storyboard feature (as shown in the middle of this page) to refresh the Storyboard images. Test Studio will run the test and take new snapshots along the way.
All the best,
the Telerik team