I am trying to export clips by range in a timeline of selects (all are multicam with two source clips). About half so far never get past 0% and eventually I have to force quit FCPX. This is the only time this has ever happened in years, and all my other librarys do not have this problem currently. I did have to use Edit Ready to join and re-wrap for import, as the researchers did not know not to disturb the camera archive. The problem appears to be random but repeatable within particular clips; there are no differences in effects or titles between those that export and those that do not.
I've tried re-installing FCPX, throwing out the prefs, copying the clips into a new project.
I was able to export the whole project as a rough cut earlier, but now I'm stuck.