When cancelling a preventive maintenance work order the recommended process is to complete the work order, if the work order is cancelled the concurrent program “Generate Work Orders” could create a replacement work order.
Another option is Navigate to Define Work Order Status Window and create a new Custom Cancel Status says "XX PM cancelled " and associate System status "Complete - No Charges" with It . Once done , Update the Status of the PM work Order that you want to cancel to "XX PM cancelled" .