Complete stab in the dark. That line in Interpreter 5 is this:
$game_screen.pictures[number].show(@parameters[1], @parameters[2],
x, y, @parameters[6], @parameters[7], @parameters[8], @parameters[9])
Your error states that there are 8 arguments but requires 9.
Looking at Game_Pictures and taking a look at the method
show, I see 8 parameters. Now I'm guessing that somewhere in your attempt to change the picture's Z value, you added another parameter to this method. Perhaps you forgot to remove this extra parameter when you went back to remove your edit?