Key duplication with key signature when editing measure properties near System Break
When changing the measure property 'Actual Duration' right before a system break where a key change happens, the key change gets duplicated, and it is impossible to remove the duplicate. Undo also does not get the GUI back to a normal state; reloading the file is the only solution.
right click on the first measure, and set the actual measure duration to '2/4' and click on Apply and Okay.
You now see 6 sharps appear.
When you press Edit->Undo, you'll see a Ghost key change on the screen in a spot where there is none. The ghost is also not played. See the screenshot.