Error exporting imovie video

The error message is saying that there is corruption at frame No. 3559 that caused the export to fail. It is probably a black frame. Expand your timeline full out and slowly scroll through it in the area of frame No.3559. Look for black frames, white flashes, artifacts and any other indications of corruption. Cut out any that you find and export again.

You can find where frame No. 3559 is located by dividing the frame rate of your project into 3559. That will tell you the time point in seconds at which the frame appears. Divide that by 60 to get the time point in minutes. So, for example, if your project is 30 frames per second divide 30 into 3559 to get 118.63 seconds as the point in the timeline where frame 3559 appears. Divide 118.63 by 60 to get 1.97 minutes as the point where frame 52275 appears. Scroll around in that area.

If you want to preserve your original project, you can duplicate the project and work with the duplicate.

Another thing that you can try is deleting preferences. 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 blank library. Reopen your old library to get back to your projects. It is a safe procedure. Now see if you can export.