×-Release the lower wraithwing
-Step onto the segment of land near the upper one

×It's the reason the wraithwing gets stuck. If you get close enough that the wraithwing views you as its target over the decoy, the wraithwing will run away, getting closer to the decoy.
To resolve this, just keep both wraithwings alive. Separate them, lead one to the snake, then lead the other along to draw the one near the decoy towards you.