When I am trying to use the Quick Reply box, the page sometimes starts shifting up or down so the Quick Reply box scrolls off the screen. Then I can't type without moving the vertical scroll bar to bring the box back.
The page apparently was taking some time to load. It was doing it for 10-15 seconds.
Maybe an ad was changing size or shape.
It was behaving like that was the case
I got a page on another site last year where the reserved space was tall and narrow, but one of the ads was short and widel by mistake. The ads rotated, and the web page parts moved all around each time the ad with the wromg aspect ratio loaded.
It hasn't happened today. It was doing it every edit for about half an hour yesterday.