Suddenly encountered this.
An Xcode 7 project contains some SpriteKit scenes. But trying to view them in Xcode causes an immediate crashing of Xcode.
The same sks files open fine in Xcode 8.
At first I thought that Xcode 8 had modified the scene files, rendering them toxic to Xcode 7. But that does not seem to be the case. Reverting the files back with version control does not solve the problem.