Throwing this out there, hoping it helps:
iMac 27″ Late 2015
FCP X 10.4
OS X 10.13.2
I have the same problem — with the SD Card with my XDCAM files plugged in, FCP X 10.4 closes within a few seconds. FCP X works fine without the SD Card plugged in.
Sony Catalyst Browse 2017.3.0.192 accesses my XDCAM files (from a Sony EX1R camera) on the SD Card without problems.
With SD card plugged in, try opening FCP X 10.4.
Error message :
Crashed Thread: 2 Dispatch queue: com.apple.proapps.xdcam.radplugin.requestqueue
Pro Video Formats v2.0.6, installed with FCP X 10.4
“Pro Video Formats includes support for…
Apple Intermediate Codec
Apple ProRes
….
XDCAM EX / HD / HD422”