When you place a Cover Order (CO), both legs of the Cover Order get placed in the exchange. If either of the leg is canceled by the order being out of the execution range, the other leg might create a hanging position that can not be cancelled by you. 

If the second leg gets canceled, the first leg of the CO would become a hanging position. Likewise, if the first leg of the CO gets canceled (because of the order being out of the execution range), it may create a reverse position instead of the expected direction. 

In such a case a reverse position is createdto reduce the risk for your hanging leg.