Final Cut Pro is mostly very stable. Crashes and Export errors are rare.
But when they do happen, doesn't it appear to be at the most inopportune time, when you're rushing to get a video to a client.
Well! here's a possible quick fix.
I've published a number of videos on other possible fixes click here for the playlist. https://www.youtube.com/playlist?list=PLP6q-
This video will show you a secret and hidden command that will Verify and Repair damaged Projects in Final Cut Pro.
Let me tell you how.
Once you've got the suspect project open in Final Cut, make sure you duplicate the Project as a Snapshot first. Then double-click the original Project to make sure it's open in the timeline.
You'll still have the Snapshot Project should it go astray.
Hold the Option key and select the Clip menu. You'll see a command that was not visible without the Option key: "Verify and Repair Project".
Select the command and if alls OK, you'll get a "No repair is needed at this time" message.
Otherwise Final Cut will try to repair the inconsistencies for you.
If you want to, now that all is working fine, delete the Snapshotted Project.
It's as simple as that.
Finally if you weren't able to open the Project because Final Cut keeps Crashing. Check out this video https://youtu.be/slEXsIadzZo