Unable to use auto layout (ctrl + drag) on xcode after some time of using
Another person, had this same problem where performance plummeted on an external display.

What I ended up discovering was that the external monitor issue was indicating that there was a UIView that interface builder couldn't quite figure out properly for auto-layout.

In his case it was a UIToolbarBarItem that contained a UIView that contained a UILabel. Once I removed the offending UIToolbarBarItem the performance issue resolved itself. It went from being completely unusable to smooth scrolling.

You should check if you have a UIView inside something that might cause auto-layout to perform poorly.