I have similar problem.
Double click or Command-4 (keyboard shortcut) does crash the inspector. Before it did crash, then it did not crashed any more, now is crashing again.
I even tried to open a clean project to see if project was too saturated. That was not the case.
In report file (which comes up when fcp x crashes) this is the information I was able to gather:
.
*** Terminating app due to uncaught exception ‘NSImageCacheException’, reason: ‘Cannot lock focus on image , because it is size zero.’
…
What does it mean, it is size zero??
This is weird specially as inspector works otherwise, and did work before fluently.
How can the program change itself while operating??