Paul,

I don't know if each relay is dedicated to a bank of locks or if they together handle the entire switching load.

Jerry is also correct, it could be a bad solenoid. If it unlocks but doesn't lock or vice versa you can rule that out I would think so you do not have to tear apart the door. If you think it is the solenoid to verify it I would suggest ohming out the circuit using the wires going into the door before tearing the door apart. The resistance can be compared with one that works.

Only Jerry (who gets his oil for free) would use enough lube oil to leave a trail before he figured out the solenoid was bad.