Can't open the final waterway. Stuck.
I'm currently stuck and can't seem to open the final waterway. The game lets me push the button (as seen in screenshot), but the door to the waterway won't open. I think I've done most of the quest stuff, because I've reached the part where you put all the glowing pieces on the large robot up north. I only need to open this waterway so I can get the last shining piece. I fear that I've stumbled upon a bug. Either that or I'm completely missing something else.
Please see this link for the images: