We have setup one page navigation but when the user clicks on a link using an iPhone the navigation doesn’t take the user to the right location on the page it seems to miss by around 150px so they see the bottom of the last section.
Please try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.