Website playback not functioning properly

On the larger of my two uploaded scores, the website audio playback stops at last bar of a previous version, but I've since added measures to it. The score playback at that point goes faster than it's supposed to and stops randomly at 7:17, which is not where it should be. Both work on the app (as well as they can on my iPhone 6), and I do realize it's a pretty big score, so that could entirely just be a overload problem.