OK, I worked around it easily.
I thought you had two different "variables" to check state, so you could see if a flashing object was already invisible (in my "weltanschauung", the flashes of the invisible flashing man are invisible).
I use to employ "turn invisible" to get rid of objects without destroying them despite of events they could activate.
Well, this feature has an advantage. I can make the object visible by simply making it flash, so I can save the "make visible" action.