KUKA Sim Invalid field index


I’m trying to set some I/O with a KUKA robot. It all worked fine untill I added another function and I now get the message: “Invalid field index”.

What does this mean and how can I fix it?

Do you have any Arrays, where the index got bigger then the declarated Array?
Thats a problem i got, when my Array goBack[30] got an further Element goBack[31].