Warning mark gets stuck and is not drawn in scrollbar

When the window is tall enough to fit all the text, the orange warning mark that is normally drawn inside of the scrollbar gets stuck and won't disappear.  Its horizontal position is unchanged, and is no longer drawn where the scrollbar should be.

If the window is not tall enough to fit all the text, and thus a scroll bar is necessary, then there is no problem.

See the attached animated GIF.