Yeah so the error is actually happening either pre-script generation, or during. The null pointer is being thrown by the Java environment. So one of their methods is trying to operate on a piece of data that no longer exists. This may be stemming from a failure to correctly name the variables, as you’re describing, but you can’t really DO a whole lot with variables on the Java side, so I’m not sure. Just seems like every time I’ve seen someone post about the null pointer here, they are also always using subprograms, so I’m assuming that’s the underlying cause. Unfortunately, this issue still hasn’t been fixed, as you can see from this post (Java Null Pointer Error on Palletizing Node After Restart) it was reported as far back as 2021. (also here Palletizing subprogram gives error when clicked on 'Keep subprogram updated')