Lock orientation of camera at capture

I take tens of thousands of photos with my subject directly below the phone. Orientation lock does not lock the camera orientation when taking the photos, that I've found. The images are orientated in random directions depending on the mood of the phone regardless of setup or angle of the shoot. Is there a way to lock the camera orientation, not the screen orientation? This has frustrated me for several generations of iPhones and iOS updates.

Please do not respond with screen lock suggestions because they are not the problem. The problem is the orientation of the camera when pointing straight down. The camera becomes confused and orientates the image at random, regardless of screen lock.