OK, thanks. That’s a different crash (obviously), so this is getting even more mysterious. The most puzzling thing is that 4.17.0 worked OK. I don’t have any good ideas at this point. One thing you could maybe try is to use First Aid in Disk Utility, as maybe there’s some permission issues with the UE4 folder structure. Or try restarting the Mac. It’s shooting in the dark, but considering the lack of better ideas, I think it’s worth giving a try.