Sorry about my poor english first.I'm a new developer.When I use the storyboard to create by userinterface in xcode.There is a error showed at the top of the interface builder. It says "An internal error occured. Editing functionality may be limited " and there is a button at the end of line "reoprt a bug".After this error showed ,the storyboard got very slow and unstable.At first,restart the xcode will solve this issue temporary.But one day,it showed again,I restart the xcode as usual.The error line is gone, but the interface builder didn't restore.It stuck forever,not just for this project,create a new project is the same😟I searched other questions but they don't get the solution either.Can anyone could tell me how to solve this probelm?PS：I don't know if you can understand my question,maybe I don't make the question clear.You can read this question from the link at the bottom,this guy has the same problem,and no solution.Other questions like me:https://forums.developer.apple.com/message/88935#88935