Weird Bug

private moveUp(competence: Models.Competence) {
            var id = this.getIdinParentChilds(competence);
            if (id > 0) {
                var childs = competence.parent.children;
                childs.splice(id, 1);
                var comp = new Models.Competence(competence.id, competence.description, competence.parent, competence.children);
                comp.edit = true;
                childs.splice(id - 1, 0, comp);
            }
        }

        private moveDown(competence: Models.Competence) {
            var childs = competence.parent.children;
            var id = this.getIdinParentChilds(competence);
            if (id < childs.length - 1) {
                childs.splice(id, 1);
                childs.splice(id + 1, 0, competence);
            }
        }