That’s coming from the defaultBeanProcessing() method in JSONObject: https://github.com/aalmiray/Json-lib/blob/9e2b3376ee8f511a48aa7ac05f75a7414e02280f/src/main/jdk15/net/sf/json/JSONObject.java#L729
It seems like JSONObject is tripping up on the GString. My guess is that it doesn’t see it as a String, and therefore attempts to treat it like a bean. I couldn’t verify this theory because for some reason json-lib is not resolving for me via @Grab. But, try doing a toString() on that GString.