This is not in code but in IB. It happens when the second view controller presentation is set to "Over Full Screen". I managed to fix it by setting the Navigation Bar appearance

It happened to me too. I've managed to solve it by deleting the iOS DeviceSupport files. You can try it by closing the Xcode and delete all files in $HOME/Library/Developer/Xcode/iOS DeviceSupport, then relaunch Xcode