You can see my troubles in this video:
This happens when scrolling down from the top, and scrolling back up from the bottom. I also just found that it happens on another site of ours. Both were made with earlier versions of Pro v3. The site in the video clip had some blocks copied into it.
I found a few other forum posts with similar problems. Some suggested setting heights to auto, but that didn’t seem to change anything.
Other posts suggested bad HTML code. I looked through as much as I could, but didn’t really find much.