Original iMac Pro, 64GB RAM, Vega 64, 28TB Promise RAID, macOS 10.15.6, FCPX 10.4.9.
A single 1 hour and 17 minute duration documentary project inside 285 GB library, with only two Events.
I can access all media in the Browser and play it all in the Browser just fine.
When I click on the Project, I see the preview icon in the Browser just fine, but for only two seconds, then BANG!
Unexpected quit, crash, done.
I've trashed renders and prefs.
This library is being updated from an FCPX 10.4.8 version. Going back to 10.4.8 could be possible if I had a copy to download from somewhere. This system was updated before I got this Library to work with.
I can email anyone a copy of the full crash report, but here's the part usually used for troubleshooting. I see the TwinFX by Coremelt mentioned, and I see "unversioned libcrypto dylib" mentioned, but no clue what that is. Is this really Coremelt specific?
Process: Final Cut Pro 
Path: /Applications/Final Cut Pro.app/Contents/MacOS/Final Cut Pro
Version: 10.4.9 (376482)
Build Info: ProEditor-37648002018000000~2 (16A312)
App Item ID: 424389933
App External ID: 837325800
Code Type: X86-64 (Native)
Parent Process: ??? 
Responsible: Final Cut Pro 
User ID: 501