Why is scrolling slow in IOS, but everything is fine on Mac?

Question

iOS

Good day! There is a problem with scrolling in Safari on mobile devices (iPad, iPhone) on postav-wordpress-3.tw1.ru . Scroll slows down. Everything is fine in Safari on Mac. Can someone point out what is the reason or where to dig?
Engine-WordPress. Bootstrap.css has the -webkit-overflow-scrolling:touch property;