On Fri, Apr 26, 2019 at 3:26 PM Eli Zaretskii <eliz@gnu.org> wrote:

So the window-start marker belongs to the wrong buffer.

Was standard-reading.org the buffer displayed in the selected window?
Did you switch buffers right before the crash?

I am a bit hazy in my memory regarding that .. it's very likely I did that. All I can tell is that I was quickly scrolling/switching windows when this crash happened.