Sound out of sync after export
Sound went out of sync on export of vertical video with “1080p March sequence” settings. Even though iPhone video records at 4K24fps, Rush thinks the “matched” frame rate is 30fps.
As of build 1.0.1 Rush iOS only supports exporting to 1080p30. That's why you're hitting this issue. We're working hard to get 4k exports into the app. In the meantime, you can sync your project to desktop and export 4k from there.
Sorry for the inconvenience and thanks for the report.