You can see it even in your online demo https://ajaxsearchpro.com/isotopic-layout/ but it’s more evident in my site http://www.gardalake.net/
Isotopic layout pagination is not behaving properly on mobile (iphone, iphone simulator, galaxy s8 are the device I used to test), when you select any results page >2 and you scroll up, the page will be automatically changed again to results page 1
Scrolling very slowly doesn’t always trigger the problem