Steps to reproduce:
- Create a new dashboard.
- Create Action Log widget (with unchecked "Show header" checkbox) in the top-left corner of the dashboard (or any other place starting with the top row).
- Save the dashboard and enter a kiosk mode.
- Focus the widget by mouse. The page will slide down to allow the header to appear.
- The vertical scrollbar will also appear causing unnecessary flickering.
The scrollbar should appear when there is actually a scrollable content.