Try to restore a previous version of the original library from a Time Machine or other backup. If the new library and project work as expected, you've isolated the cause of your issue to the original library or project.
HOW DO I EXPORT IN IMOVIE 10.1.2 720P
Choose File > Share > File, click Next, name the file "Finish Line," then save the video file to the Desktop. Just one note Even though iMovie may export project with a 720p or 1080p resolution, the DVD is going to be able to output 720×576 (PAL) or 720×480 (NTSC) at best.Choose File > New Trailer, click the Action trailer template, then click Create.In iMovie, click Projects to return to the Projects view.Next, create the test project using a built-in trailer template, then export it as a QuickTime video file: Name the test library "Test iMovie Library," then save it to the Movies folder in your home folder.In the Open Library window, click New to create a new library.While you press and hold the Option key, click the iMovie app in the Dock or double-click the iMovie app in the Applications folder.Motion templates available from can create a new library and test project to check if the issue is with your library, project, or iMovie app.Performance tests are conducted using specific computer systems and reflect the approximate performance of MacBook Pro. Prerelease Final Cut Pro 10.6 tested using a 5-minute project with 8K Apple ProRes 422 media, at 8192x4320 resolution and 29.97 frames per second.
HOW DO I EXPORT IN IMOVIE 10.1.2 PRO
Testing conducted by Apple in September 2021 using preproduction 16-inch MacBook Pro systems with Apple M1 Max, 10-core CPU, and 32-core GPU, as well as production 2.4GHz 8-core Intel Core i9-based 16-inch MacBook Pro systems with Radeon Pro 5600M graphics with 8GB of HBM2, all configured with 64GB of RAM and 8TB SSD.Prerelease Final Cut Pro 10.6 tested using a 5-minute project with 4K Apple ProRes 4444 media, at 3840x2160 resolution and 23.98 frames per second, transcoded to Apple ProRes 422.
Prerelease Final Cut Pro 10.6 tested using a 1-minute picture-in-picture project with 7 streams of Apple ProRes 422 video at 8192x4320 resolution and 30 frames per second, as well as a 1-minute picture-in-picture project with 30 streams of Apple ProRes 422 video at 3840x2160 resolution and 29.97 frames per second.