How to change page shift view in Preview for mac?

When I scroll down using the touchpad on my mac, Preview suddenly shifts to the middle of the next page of the PDF document. It didn't use to be that way. There was no sudden shift, and I was able to scroll down smoothly to the beginning of the next page. Any suggestions to set it back the way it used to be? It doesn't seem to matter if I open the PDF with the Books app in Preview or the Preview app by itself.