Still having sporadic crashes. I've tried uninstalling command post and a day or two will go by with no crashes - and then I get them all day long. I'm about to go into an intense period of editing and I'm very concerned about how reliable FCP is being.
Unfortunately no further details or resolution were posted. I don't know if that forum allows contacting other users but you could consider that. Maybe that person has more info about the resolution -- it wasn't that long ago.
You might want to consider erasing your entire machine and reloading your apps and files from scratch, only installing what you need. IOW no extra apps or drivers. I Know that's a lot of work -- I just did it a few weeks ago.
Today there is a FCP bug fix release, 10.5.4. It addresses a stability issue when exporting with certain MacOS language and region preferences, also a stability issue when playing H.264 and HEVC media. I suggest you update to that.
When a new version is just released you may need to go to the Mac App Store, search for Final Cut Pro, then click the *name* "Final Cut Pro" to reach a page where they allow downloading the update.