When the lightbox opens it opens with position top 50% which means it's in the middle of the page
When the iframe opens it scrolls the window to the top. This together with the point above means that the user is taken away from the actual lightbox and has to scroll back down to it. This is caused by the AcceptUI doing a window.scroll(0,0) at lightbox open.
I cannot have more than 1 payment button on one page because the AcceptUI click event attaches only to the first button in the page which has the class AcceptUI.