Well that was weird. It made me wait for absolutely ages for the soft earth to appear. I didn't need to drag my villagers around to see it, it was a visably lighter track of earth going from the left of the reservoir to the stream. It was not there when I asked for help on this, and I spent days dragging my villagers all around for no aparent reason. I wish I’d been told that something needed to trigger that patch of lighter ground appearing, instead of having to flail around for ages. I still have no idea what even triggered it showing up! It seems as if it waited until I collected my 35th piece of Red Wood, which makes no sense, since I didn’t need anywhere close to that amount to complete the puzzle. Other than that, I guess I remain clueless.