If you click an drag one of the page thumbnails, hold and use a scroll wheel to for example scroll to the end of the list and let go it will have moved a different page then the one you selected (see video). Sometimes it works but a lot of times it moves the wrong page. You can see it happen twice in the recording.
Also I think the way it indicates where it will place the page is bad. You can hardly see it becuase its so dim and just a line next to the thumbnail. Why not rearrage the thumbnails while dragging or at least put a more visible line.
This is on the latest version 1.8.3 on MacOS 10.15.4. I am using a Logitech MX Master mouse.
https://recordit.co/JZla63kQtV