Pretty photo not working properly?

Question

css

Hello! There is a simple site with a photo gallery. Pretty photo library is used to view photos in full size.
But it turns out that the picture "shifts" if there is a scroll on the page.
Page where it works fine: test.reg-school.ru/photogallery/album-18783/photos
Page with an error: test.reg-school.ru/photogallery/album-44950/photos