I hadn't even noticed that option before! It also crashes for me on OSX. I'm sending the info to their support. Report says
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: EXC_I386_GPFLT
Seems like something's calling something it shouldn't, but other than that, I don't know much. You can export the reduced STL from File -> Export Model and then remove the original one, then import the saved (reduced) model and then it works fine. Seems like maybe something in memory is looking for information that was removed in the mesh reduction?