That's a very good start.
You were trying to reconcile the predicted and measured lengths of the LM shadow. I remembered from something a few months ago when I was looking at the elevations from Google Moon. The LM is in kind of a depression. So I checked the elevations again. Sure enough, the surface rises five feet from the base of the LM to where the shadow would have ended.I'll bet your difference is right there.
Note: the surface continues to rise another foot to the west, then levels out and gradually slopes down. This is entirely consistent with 5931, which you show on your page. We're seeing just to the top of that slight north-south rise, creating a false horizon. That's why the shadow almost reaches it.