can anybody tell me why this error is displayed when launching bus editor

I am getting this error when launching the bus editor 'error using ==> subsref the specified key is not present in the container'

Does anybody have a idea why this error occurs. I have a huge bus object with lots of inner bus objects (elements with bus object datatype and they again have bus objects inside).

the reason might be because of too many number of bus objects? or maybe the repetition of bus object elements or names?