invalid objects after upgrade from 11.5.10.2 to 12.1.3

customer got invalid objects after upgrade from 11.5.10.2 to 12.1.3
PO_MASS_UPDATE
BODY PO_MIGRATION_PKG

SQL> alter package PO_MASS_UPDATE
 2  compile body;

Warning: Package Body altered with compilation errors.

SQL> show error
Errors for PACKAGE BODY PO_MASS_UPDATE:

LINE/COL ERROR
-------- -----------------------------------------------------------------
17/11    PLS-00323: subprogram or cursor 'PO_UPDATE_BUYER' is declared in
        a package specification and must be defined in the package body



SQL> alter package PO_MIGRATION_PKG
 2  compile body;

Warning: Package Body altered with compilation errors.

SQL> show error
Errors for PACKAGE BODY PO_MIGRATION_PKG:

LINE/COL ERROR
-------- -----------------------------------------------------------------
453/4    PL/SQL: SQL Statement ignored