Final Cut Pro X crashes when exporting a project

If i have a project that I want to export, I'll pick "File, Share..."

If i choose "Masterfile" , "Apple Device" or "Export File" , FCPX crashes immediately.

If i choose DVD, Facebook, Vimeo or Youtube it will export just fine.

I'm running FCPX 10.4 and had the problem. Then updated to 10.4.1 and same problem.

OSX 10.13.6 (I can't upgrade my system to any higher os. 2009 iMAC)

I did a fresh install of OSX on a separate partition and have no issues exporting.

So if I want to export a project, i have to reboot to this partition and then export the file. Pain in the butt.

I tried reinstalling OSX on my main partition using recovery mode, but it didn't help.

I really don't want to have to wipe my entire system.

(iMovie does NOT have this issue. I can export a project just fine using any option.)