Had a cato yesterday. Blew the rear closure out at about 50'. Bulged the threads at rear of case, now garbage. Could not find the rear closure. Aeropack retainer ring bent up, found that. About 1/8" of 2 of the grains are still in the case, almost like the grains separated. Delay not burnt. Liner intact, no burns or breaks. Seal disk o ring good and still in groove. Forward o ring in place and ok. Any ideas??