final cut pro x crashing when exporting

Start by telling us what OS you are using and what version of FCP; also what media, what drive, how much free space.

Often when this happens there other software problems, which we can't know about without more information.

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

You might have a problem with an iTunes update. Older systems seem to be effected by a change in the mobiledevices.framework.

See if this thread helps you.

https://www.fcp.co/forum/4-final-cut-pro-x-fcpx/32665-fcpx-crashes-on-export?start=20

While we wait for that report: how long is the video, and how are you exporting?

Make a new project, add a short clip, export. Still crashes?