Whenever I type, for each key I press, my screen shifts downward to a certain point, then resets back at the top of the New Reply box and starts again for every eight or so keys. It is very reminiscent of a typewriter, but it is very annoying. Also, I can't look at the very top of the page to hit the subs button.
My S7 was doing that too, but I don't have the problem on my iPhone 5 (which I'm using now).