200-500 doesn't tell you much because it's an E lens and this looks like a mechanical aperture coupling problem. If you still have the D7500 or any other Nikon body, try the 50 on it again now and see if it still works. I guess you don't have any other lens with an aperture ring? Without testing another lens that isn't E or G, or testing another body, you won't know if the problem is with the lens or camera.