LM5118 short-circuit protection question

I am design a DC/DC power module use LM5118 ，VIN 9-48V ，Vout 53V/0.5A ，NOW when i  slowly increasing the load（<0.5A), there is no vout suddenly，and LM5118 is damaged， always feet 16 and 18 feet breakdown，then i try to put a   schottky diode between  16 and 18 feet and increase the load，feet 10 breakdown，pls help check my SCH and give me a hand。thanks！1222.LM5118设计原理图.pdf