Error: ORA-06508: PL/SQL: could not find program unit being called

I’ve created BizAPI and custom API for import XML file.

The custom API will call Register PO Receive standard procedure

(ex. Receive_Purchase_Order_API.Packed_Arrival__).

After I put the XML file in filerep1\<instance>\in folder, the file is imported correctly.

But the custom API raise error “Error: ORA-06508: PL/SQL: could not find program unit being called” when call other module’s standard procedure. 

I’ve tried re-execute the same procedure which is called in custom API via PL/SQL command with different users (ifsapp, ifsconnect, granted users), the error is not found and can be processed correctly.

Could you please suggest me to resolve this problem correctly?