I was taking pictures during a kids indoor performance with the EOS R and the 300mm f/2.8 IS II. The camera was set to Av with auto ISO and a min shutter speed set to 1/250s. For a while, it was working fine, but then a spotlight (I think) turned on, and the electronic viewfinder was overexposed by 3 stops or more. However, it never adjusted, and the viewfinder remained overexposed. I took a picture and reviewed it on the back of the camera, and it was overexposed like the EVF. I then set the ISO to 3200, and the viewfinder/pictures were back to normal. I wish I had saved that picture... Has anyone else have a similar experience?