Xcode storyboard: Internal error. Please file a bug

Question

While editing in the storyboard, specifically assigning a view controller to a specific class, I suddenly encountered this error when I wanted to run the project.

Ma

Answer 1

I'm using Xcode 9.2 and all the above answers didn't solve the issue. My issue was that i added a constraint accidentally to the TableViewCell Content View. And content view is not constraint applicable and i'm not supposed to add constraints to it. It is already locked. But i really don't know how i added constraint to it accidentally. After deleting the constraint everything started working again perfectly fine.

I thought this answer would help somebody having my same issue.