Xcode 8 hangs / unresponsive when opening storyboard

Question

I\'ve recently upgraded to Xcode 8 and updated my project to Swift 3. All worked fine for a little while. Storyboard loading has always been slow (even when still running Xcode

Answer 1

I just upgraded to Xcode 8.3 and this storyboard hanging issue came...I've tried all that mentioned above, none of them works.

Finally I noticed there's some auto-layout warning saying that one of the navigation controller scene's navigation bar size is not correct. It insists that its width should be 320 while the chosen device is iPhone 7. I switched back to Xcode 8.2.1(8.3 is just too slow to change anything!), then changed the viewing device to iPhone SE...all fixed!