Before buying relays, I wanted you to swap them to verify that it was a relay......if the problem moved from one position(lock or unlock) to another, then it was a relay......since it didn't change, it is a circuit problem
So, looking back at the circuit, at rest, both relays ground their respective circuits....when either relay is energized, it goes from grounding the circuit to powering the circuit.....
Since the circuit blows when you hit the "Lock" button, the circuit side(of the lock relay), not the switching output side of the relay, is being grounded/shorted........Diagnosis begins at the I/P fuse block because that is where all three circuits in parallel are joined.....one of those circuits is grounded, and pulling out the fuse block may give a visual of a cut/grounded wire......but those wires go all the way to each of the doors and to the hatch, and if the short is anywhere in those wires, it will cause the fuse to blow........
This is why it only blows in one direction.......since both relays are grounded at rest, there is no problem......when you power one relay, it sends voltage through the wires to the three solenoids, and then the ground at the other relay.....but if that relay circuit is shorted to ground already, there is no problem......however, when we want to go in the opposite direction for the locks, the relays reverse, and the one that was previously powered, is now grounded, and the one that was grounded now provides power....but the first thing it sees before the solenoids is a short, and this blows the fuse.....hope this makes sense....
And like I said, unless a visual inspection shows something obvious, you will have to separate the three circuits at the fuse block to test for a short in each circuit.....this can be done with an ohm meter or a powered test light....