Verification is ok. I've got an extracting progress bar there a while. When it goes around 70% system crashes without any warning. Very strange though.

Did you try to quit all apps before extracting xip? If not, try it first. Quit all apps then double click on xip file and wait until extract complete. Do not launch other apps especially Safari and Xcode while extracting. I suspect there is memory corruption problem during extracting, probably some libraries.

Oh I see. I think I should admit that I didn't understand wrapped value stuff at all. Everything is clear now. Thanks!