I own a Nikon V1 camera. It is considered to be quite old and outdated these days, but still I find it useful from time to time.
Few days ago I had this strange problem: when I turned on the camera, things were shown properly on the display, but when I put my eye on the viewfinder and then removed it again the image stayed on the viewfinder and refused to go back to the display.
Took me quite some time to understand that the sensor on the left side of the viewfinder was simply covered with too much dust. It tricked the sensor to think that my eye is all the time on the viewfinder and therefore showed the image on the viewfinder instead of the display.
I though it might be useful to share this information in case one of you out there is still using Nikon V1 and experience the same problem. Of course that cleaning the sensor solved the problem.
Here is where the sensor is located: