Angry Birds from Rovio…
when login dialog is opened automatically by app
if you open from login dialog another app, such as browser edge to read information from rovio site by clicking a link on the dialog. Looks like repaint thread is blocked by a modal dialog…
Another example: Install an app from Aurora store. When it is installed you will see installed button on app page in Aurora store. Open an App by clicking on that button. The app will be opened.Now look at the SailfishOS ribbon with opened Apps. You will see black rectangle.