Your page has some elements given 100% of the browser height which is being set using JavaScript. Hotjar takes page screenshots in a single large window, these types of elements keep enlarging as much as they can, rendering incorrectly.
Solution: This can be fixed by setting a maximum value your height calculation (this can be a value you choose, up to 1200). As long as there is a limit, it will fix the problem.
viewportHeight = (viewportHeight > 1200) ? 1200 : viewportHeight;
// - or - //
if (viewportHeight > 1200) {
viewportHeight = 1200;
}