As designed Responsive full screen image

[Hornstar]

I just clicked on an image to see the image in full screen and it made the screen go strange and I could not get the screen to go back to normal without getting out of the thread.

 

[Mike]

This is the same behavior on the desktop - clicking the image again will shrink it.

However, it's possibly not as useful in this situation as the user can zoom instead. That said, it's possible to have situations where the browser is small and zooming isn't possible or the browser is large and zooming is possible so it's something that's hard to detect and probably not worth it IMO.