I am experiencing similar problems. I have attached the factory file I am trying to slice.
S3D also crashes for me when I try slicing the file posted by StafDehat.
Simplify3D 4.0.1
MacOS High Sierra 10.13.4 (iMac) and 10.12.6 (MacBook) – the crash happens on both machines.
I have tried rrdavis' suggestion to re-download and re-install. This has not solved the problem.
I should note that the MacBook managed to slice the file
once. When I left Preview Mode and sliced the file again it crashed once more.