The autosave is a feature of Atto that I believe was added in 2.8. It saves a draft copy based on context after the interval defined in the settings. If the browser window is closed prematurely, this copy is reloaded in the next page the user opens with the same context. If the page is saved or cancelled with a button at the page bottom, the draft copies for that context are deleted so that there is a blank editor the next time.
I have not notice the problem with editing questions, but I suspect that it is because the user instead of saving is using the button "Save and continue editing" then checks the preview, and closes the window instead of saving the question again. This may also be a new feature. I just noticed it recently.
You might encourage the save with the other button. Otherwise, a unwanted draft file can be removed from the editor with ctl-z or the undo button.