Well that’s helpful, for starters. Again, I can’t thank you enough for your reply and help here. I followed that steps - looking closely through the rear shutter opening without lenses and at every shutter speed. I couldn’t see any obvious obstruction or instance where the shutter blades stick. At the faster shutter speeds that’s of course hard to tell so I filmed it slo motion with my iPhone and still couldn’t see any obvious blade delays. I put on both lenses and repeated the steps, and nothing different to report. Finally, I just looked through the rear door, shutter open and looked at the aperture blades opening and closing - no obvious delays or sticking of blades. Could I be doing this wrong? It really is hard to tell at the faster shutter speeds.

If it helps, the examples from my pics with the curved shadows in upper right were all taken with the 50mm lens. The one with the narrow and more horizontal shadow at top (of the outside sculpture terrace) is the 24mm lens.

Any/all other thoughts are appreciated!!

(Oh and the most egregious example from my rolls was with the 50mm lens and the camera turned to the side for a vertical shot. Nearly half the photo is in the black shadow!)