Only one entry can be set as default for a given object in one company. E.g. if there are two entries for object EMPLOYEE in company 1, only one should be set as default.
See the comments for the transaction /PACG/ECM_SAASG – the analogue logic is applied for personnel area dependent object.
Originally the object "EMPLOYEE" has been made Plant dependant which was not quite correct. In order remaining compatible this has been kept. Correct is, that the object "EMPLOYEE" is dependent from the personnel area.