I have two Gyre 250s and on one, one side is rotating down by itself and stirring up my sandbed. It happens every once in a while. I took it out this last weekend and gave it a good vinegar bath and after I put it in the tank the other side rotated up on its own and blew water out of my tank for about half hour. Needless to say it was a big mess. Both side rotate more freely than my other 250. What can I do to stop this?