Steam Mill near the Mormon Hollow Spur

I didn't find much on this last hike before big game rifle season starts. I resorted to following some stone walls in an area that looked promising. After hiking for quite a while (and kicking up a sleeping deer in a warm spot along a clear cut, now overgrown), I found two rock piles near a stone wall.That stone wall in the background is typical of the walls I was following.

A close up of the upper rock pile:Looking in the opposite direction, downhill, over the two rock piles:
When I crossed Mormon Hollow Spur and headed uphill, I found a very different looking rock wall. At first, I thought "cairns", because I could see the very obvious gap between the wall, making it look like separate structures. Walking up to it, the sun just above the wall (in the morning) created a dramatic effect, but didn't do anything to help the photos turn out better. A cloudy day would have been better. These pictures were taken with the sun to my back, opposite the way I walked up to the wall.
I believe that gap was created by part of the wall tumbling down. But I can't help to ask myself, why was the wall constructed that way? Wouldn't one over two and two over one prevent this from happening?

The end of the wall on the eastern side (near the gap):
The end of the wall on the western side (far from the gap):

As I walked down Mormon Hollow Spur to get back to my truck, I found this along the side of the road, in an area slated for logging (note the blue paint):

I have a couple of videos, but I'm having trouble getting them to upload, so I will try to put them in a separate post.