I added an attachment to help understand what I'm saying. I do not use opengl layout, I'm using pdfLayout.
This strange behavior only happens with different_page_size flag true, if I use the lib without this flag, the vertical move happens normally, that is, I zoom in from center of the page then I scroll the screen top or bottom to reach the start or the end of the page.
Using different_page_size this do not happen. After zoom, my vertical move is blocked, I still can scroll horizontally but not vertically.