If this is a bug (and I think it is) it is relatively minor. The problem is that when you edit the action to change the target of the action to a different object type, it forgets what action type it was which might result in the loss of work.
The linked .capx contains a sprite, a text object and a mouse object. There are two mouse events, each with an action to set visibility or set position.
If you edit either of the actions and click [Back] twice and switch the target of the action from sprite to text or text to sprite, then click the [Next] button.
The default action now reverts to the first action Rotate clockwise instead of what it was originally.
If the action is a common action between the old target and the new target object of different types, it seems to me that it should keep that action the way it does if the object types are the same.
The good news is that if you notice and fix the action and you click [Next] again it does seem to remember what you had originally, so you don't lose any work IF you are paying attention. If you aren't you lose your action parameters.