Cracks that start out little (but not stress cracks) and grow and grow. They end up with gaps that open and close as you ride. In each corner. Previously, the bulk head came lose and that was re-inforced last winter. Our concern is, with a reinforced bulk head and a reinforced hull, there is obviously something else wrong with the boat....something very fundamentally wrong to have it show up again so quickly (2 trips after the "repair").