Water Fill Compartment Lock

greetings all,



i have a '76 Trade Wind that we're slowly refurbishing.



i was going to sanitize my water tanks, but i'm having a problem with the lock on the water fill door.

it doesn't want to open.

i've used WD40 and some graphite, but nothing so far.

from the "locked" position (12 o'clock), the key turns slightly to the left (10 o'clock) and stays there. the door does get a little loose, but remains shut.



any recommendations?



thanks



richard