

Try to restore a previous version of the original library from a Time Machine or other backup.When you save the movie as a file, you can add the movie to your Photos library, store it in iCloud Drive, or save it in another location. If the new library and project work as expected, you've isolated the cause of your issue to the original library or project. Try to recreate the issue you were having. For example, if iMovie quit when adding a transition, try to add a transition to the timeline.Select the clip in the browser, then press the E key to add the clip to the timeline.Select the "Finish Line.mov" file in the list, then click the Import Selected button. Choose File > Import Media, then click Desktop in the Import window sidebar.

Click projects to return to the Projects view.Next, import the QuickTime video file into a new project in the new library: Choose File > Share > File, click Next, name the file "Finish Line," then save the video file to the Desktop.

