Hi @Uma Maheswara Rao Desula​, thanks for your answer.

You're right, NullPointerExceptions occur whenever we try to access some null values; but in this case, by looking at the stack trace, there is nothing that points me to my own code. It's just Spark internals I have no control over. This makes me think there is some kind of underlying cause for this issue, but without more specific clues it's being very difficult to track.