cannot undo storyboard changes xcode

You should be able to do a simple undo from Xcode storyboard, it might be related to some leftovers...

To make a good cleanup:

1. open Xcode
2. clean product (Command + Shift + K)
3. Clean Build folder (Option + Command + Shift + K)
4. Close Xcode
5. delete /Users/(your username)/Library/Developer/Xcode/DerivedData
6. repopen xcode
7. open Storyboard, change something, try to use Command+Z

Hope it works