Hey @Cassie, Thanks for your reply. But it's not only iframe or one browser issue. It's happened to all browser even non iframe page.
It's working smoothly when i remove the top section (http://prntscr.com/245jv0a). But when i add any element before horizontal scroller section problem start again.
I have some limitation to add any extra 3rd party plugin for smooth scroll. Can you carefully check this issue and give me a right solution for it?