CBlakeston wrote:
... iTunes open playing music from a wireless media drive when I went to click on the settings.. and the 'what to do when finished' option was set to add to iTunes library. I changed that for each press to 'do nothing'. Maybe that was why? ...
In 10.3.x there was a bug whereby FCPX would immediately crash upon raising the file *import* dialog box if a certain file was in the import folder. In my case it was an .M4A audio file from iTunes. This was difficult to perceive because there was a small but variable delay in the crash. You could sometimes click on a video file, then it would crash, which gave the impression it was that file. In actuality was was the .M4A file in the import folder. The file was not apparently corrupt or damaged.
Since the import dialog remembers the last folder location, every subsequent import attempt would crash upon launching the dialog or almost immediately thereafter. You couldn't navigate to a different folder -- it would usually crash when enumerating the files in the import folder. In my case the solution was to identify and remove that iTunes .M4A file. I vaguely recollect other people had this with different files, not just .M4A.
For your *export* case, I wonder if something similar is happening? IOW something in the export folder or the composition/length/characters in the path to the export folder. You can rule this type of bug in or out by setting the default exporting to a different location containing no other files. Ideally an empty thumb drive or portable drive with nothing in it, and just export to the root of that (as a test). You want a totally different, short path to the empty export location, and (as a test) make sure there are no odd characters or spaces in the path to that location. Also make sure any export drive is HFS+. APFS should work fine but it's new. NTFS you can't write to, and for exFAT, other operations are needed to split the resource fork metadata to hidden files.