rcd tripping on cooker?

my wife bought a rubbish "range" electric cooker a couple of years ago, its gone through oven elements like there's no tomorrow, easy to diagnose- either tripped rcd or on investigation no continuity through element, however yesterday it tripped rcd, elements all appeared ok, but continuity between earth & neutral, i disconnected all feeds/return from cooker, cont. still apparent at socket,cooker switch on cooker panel still trips rcd{even with cooker disconnected}, but 13A socket on panel still works without tripping. 13A shows cont. E/N but not at consumer unit.