My Nikon D90 started having an issue where the image in the viewfinder shakes, or taps whenever I turn it on or focus. Has anyone ever seen this issue? I'm assuming that it's the mirror.
I turned VR off and also tried it with another lens. I'm confident that it's the camera and not the lens.
I was able to catch it on video by putting my iPhone camera on the viewfinder here on YouTube.