series 3 oil from hand brake

hi had problem with oil from hand brake so today i stripped down the drum etcc replaced the oil seal behind the hand brake back plate and new gaskit onthe oil catcher and the felt washer, all good put back together (not fun upside down lol) re filled with oil and now the leak is back its leaking from where the hand brake back plate bolts on is there supose to be a gaskit there any ideas pls