iMovie keeps on failing when exporting

Hi, sarah-janeb,

Try deleting preferences, as that often cures export issues. Open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects. Now see if you can export. Possibly you may need to reboot to set the changes.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

You can also try placing your media into a newly created project and see if you can export from there.

If you are exporting to an external drive, check to confirm that you have sufficient space on the drive to receive the movie.

Since the export aborts at about the same place each time, it is possible that there is a corruption frame or clip at that location. Use the slider above and to the right of the timeline to expand out the timeline. Then scroll slowly through the area well in front and after where the export stops, looking for black frames, white flashes, artifacts or anything that might indicate corruption. Cut out any that you find and try again to export.

You mention that you are getting lagging and overheating. Possibly you need to reset your System Management Controller. It is easy to do. However, it is not available if your Mac is using the new M1 silicon chip.

Here's a link for instructions:

Reset the SMC of your Mac - Apple Support

You can also try resetting the NVRAM or PRAM.

Reset NVRAM on your Mac - Apple Support

-- Rich