MFPLI00012S If any ENTRY of a PROCEDURE has a RETURNS option, all entries must have a RETURNS option. A PROCEDURE cannot be both a subroutine and a function.

Whan a procedure has multiple entry points all the ENTRY statements must have a RETURNS option if and only if the PROCEDURE statement has a RETURNS option.
Resolution:
Either add RETURNS options to all ENTRY statements or remove the RETURNS option from all ENTRY statements.