Hey Paul,
The roof is missing in the mesh, because the mesh is based on the ground points only, as marked in brown in the following image. When the orthophoto is made, the pixels in the images are projected to the ground.
I would like to avoid masking each individual photo, since there are 712 photos in the project, and I have to make 4 more projects of the same size, so it would take too long.
MINE