Same problem. Think it started when I had 2 drives (one a thunderbolt i/o and the other usb) plugged in at same time. One drive was an exact duplicate of the other. — I was doing a redundant backup to keep the data safe!
FCPX got confused, only loaded some of events from one of the drives. Now even with one drive only plugged in, the events sporadically show up and when they do load, the files are unlinked.
Since I have many projects, many files, this seems to me an obvious BUG.
Surveying online forums, many similar postings are out there.
No simple feasible solution exists for cases like mine where the folders sit on drives that have thousands of other files and folders that might be causing conflict.
Conclusion: FCPX is not for me. Unstable.
But I’d love to retrieve my work. Any solutions out there?