Strange privilege error when calling a method of a ADT (abstract data type) from a view.

Hi All,I'm doing some experimenting with moving away from package based PL/SQL to Object Oriented PL/SQL using Abstract Data Types (ADT's).
I've got the following ADT that I'm using like a static class in a schema called COMMON_METHODS.

CREATE OR REPLACE TYPE SECONDARY_GETTERS_OBJ FORCE AUTHID DEFINER UNDER GETTERS_OBJ (

    /* Other code removed because it isn't relevant. */
   
    STATIC FUNCTION Telephone_Number (
        p_id VARCHAR2,
        p_phone_type VARCHAR2
    ) RETURN VARCHAR2

) NOT FINAL NOT INSTANTIABLE;

CREATE OR REPLACE TYPE BODY SECONDARY_GETTERS_OBJ AS

    STATIC FUNCTION Telephone_Number (
        p_id VARCHAR2,
        p_phone_type VARCHAR2
    ) RETURN VARCHAR2 IS