If I’m reading your stack trace right, it looks like it’s actually failing on addAproximacaoSubNode() (line 138) which would seem like it’s failing on
thisNode.addChild(aproxNode);
I would print the result of aproxNode just before that call and see if it’s coming back null or not. Regardless, I see what you’re trying to do and I don’t think it works that way. You have to implement a custom API interface to manipulate data in other nodes: URCap Sample: URCap CustomAPI