It should not matter how many times or how quickly you press the sort buttons, the Course Presentation Editor must not crash.
Go to https://h5p.org/node/221115/edit with chrome (or use the attached file)
Wait for the editor to load, click on the first slide in the slide line thing
Sort the first slide all the way to the right and then all the way back again with the console(F12) open
You'll see a JS error when sorting it back to the left again. When this happens the content is broken.
DO NOT SAVE THE CONTENT (It will completely break the content and make it harder to reproduce the problem)