In iMovie 10.3.2, exporting projects containing HEVC footage from iPhones sometimes resulted in a single black frame at the transition point. Version 10.3.3 completely patched this.
Would you like a checklist or a sample storyboard layout to follow in iMovie? Imovie 10.3.3
Do not download iMovie 10.3.3 from third-party "app archive" websites. These often contain malware designed to look like Apple apps. In iMovie 10
Because Apple ties software versions to operating systems, has specific requirements: In iMovie 10.3.2