When you go from one widget screen to another we automatically put widget to the top of the viewport for user's convinience.
This may cause the problem if your site has a fixed top bar. This top bar may partially overlap the widget.
To fix this, go to the Appearance tab in the widget settings.
Specify the Top offset in pixels.
It should equal to the height of the fixed header.
After this, the fixed top bar will not overlap the widget anymore.
Alternatively, you can uncheck the Scroll to top option to completely disable automatic scrolling.