Hello Mr Spiro
I believe you have a bug here. The API HR_EMPLOYEE_API.hire_into_job looks like it should, because it specifically looks for the person types 'EX_EMP','EX_APL' and 'OTHER'. Seems to me it ought to be allowing 'EX_CWK' as well.
In terms of working out what the form does, I refer you to a post elsewhere on here regarding the tracing of forms activity! However, I suspect it is calling PER_PEOPLE_V7_PKG.rehire (or maybe PER_PEOPLE_V15_PKG.rehire)
Kind Regards
Clive