500 Internal Server Error when using contactGroups.members.modify to add label to new person with People API

So I am creating a new contact and trying to add a new label to it on the sequence but I keep getting this error. What am I doing wrong?

        PeopleService peopleService = service.getPeopleService();

        Person new_person = new Person();

        List names = new ArrayList<>();
        names.add(new Name().setGivenName(name));
        new_person.setNames(names);

        Person created = peopleService.people().createContact(new_person).execute();
        String id = created.getResourceName();

        List people = new ArrayList<>();
        people.add(id);
        ModifyContactGroupMembersRequest request = new ModifyContactGroupMembersRequest().setResourceNamesToAdd(people);

        peopleService.contactGroups().members().modify("contactGroups/newsletter", request).execute();