I would probably favour a corroded connection on the relay socket. Removal and replacement may well clean the contacts well enough for the moment, but the thing with Corrosion is that once there it tends to carry on. If the socket can be easily replaced then that would make it nice. You could also just try replacing the relay for a new one and then greasing the contacts at the same time, just like you would a battery terminal …
Glad to have been of assistance
Mike