Hi again Otrhan,
I think your comment “big angle difference between the nadir, oblique and façade images” has explained my biggest issue!
I have taken nadir at -90, obliques at -45 and -60 but the facade images were head on, so 0 degrees, therefore way more than the 15 degrees you suggest. So the next drone mission will be to bring all angles to within the 15 degrees difference and maintain the same distances for all flight paths.
I’ll get back to you as soon as I can. And thanks again. Good to have a font of all knowledge to hand!
Paul