Right after entering the Focus mode the visual cannot render itself correctly.
Some of its space on the right appears empty. This space is not utilized.
In order to force the Gantt chart render itself correctly taking the full space available, a user has either to restore and maximize the browser window or to collapse and expand the Filters pane. These actions result in correct visual rendering fully utilizing the available space.
Steps to reproduce the issue and the pbix file are in the Issue_Description.zip file
Issue_Description.zip