If you try to return a object by reference, many things can happen.

Next Fire a C5 crash:

LOCAL oReference
	WITH CREATEOBJECT("RootObject")
		.ReturnAnObject(@m.oReference)
*		? m.oReference.myReference.Class
	ENDWITH

DEFINE CLASS RootObject as Custom

	FUNCTION ReturnAnObject(oObjectRef as Object) as Object
		oObjectRef = CREATEOBJECT("subObject")
		oObjectRef.myReference = m.This           && line C5
	ENDFUNC
	
ENDDEFINE 

DEFINE CLASS subObject as Custom

	myReference = .NULL.

ENDDEFINE

but with these workaround C5 is not fired:

LOCAL oReference
	WITH CREATEOBJECT("RootObject")
		.ReturnAnObject(@m.oReference)
*		? m.oReference.myReference.Class
	ENDWITH

DEFINE CLASS RootObject as Custom

	FUNCTION ReturnAnObject(oObjectRef as Object) as Object
		oObjectRef = CREATEOBJECT("subObject")
                dummy      = m.This
		oObjectRef.myReference = m.dummy
	ENDFUNC
	
ENDDEFINE 

DEFINE CLASS subObject as Custom

	myReference = .NULL.

ENDDEFINE