Maybe motion blur has something to do with it? I've been using photogrammetry techniques occasionally, when I needed it, in film/3d work. One thing I didn't try out, and what I wanted and you've reminded me of it now is to try going through a space with RED camera, crank the shutter so to eliminate motion blur and maybe even go with the HDRx option (for textures, later on). I'll see what Photoscan comes up with.