XPC connection interrupted in Xcode 7 for iOS 9

The problem lied in the storyboard for me as well. I created a new project and laid out the views and everything seemed to be working fine. I found these couple lines in the storyboard source (right click on storyboard and select view as -> source code) which weren't common between the working version and the broken version:

<keyCommands>
    <keyCommand/>
</keyCommands>

I have no idea what those lines are supposed to do, or how they crept into my storyboard file, but they were what was crashing the app so hard that the phone had to restart. I removed those lines from my main project and everything worked again.

This error can be caused by executing a loop repeatedly. In my case it was a 'for' loop in which I reset the counting variable. As soon as I added an NSLog in the loop it was obvious.