Mutual overwrites occur in answer workflows when a user manages to open multiple browswer instances/or tabs on the same exam.
In case there was an mutual overwrite, the position as provided by the instance attributes might deviate from the position, based on which the actual form data was generated. So, for validating and updating one has to change the position to the one from the form data (when this differs). Note that the randomizer depends on property "position" as well.
The new version avoids that the user might accidencially overwrite his data and closes on mutual overwrite automatically the older instance window.