1. Make a brush stroke with the pencil tool
2. Shift click a bit to the right to create a line from the last point of the brush stroke to to the current mouse position.
3. Undo with ctrl+z.
4. Shift click slightly above the current mouse's position.

You will get a line from where the undone stroke ended, rather than where the stroke before it ended. I think it's a bug because it does reset the point when "cancelling" a stroke using the opposite mouse click button. The black stroke in the image below shows the undo with control+z not resetting the point, while the blue stroke shows the point getting reset.

Aseprite 1.1.4-beta1