Success Factors: re-open a requisition from SAP

Hi - I'm having some trouble re-opening requisitions in SF from SAP.  Integration is switched on.

So we've sent a requisition over to SF, completed it, and set the vacancy as filled in PD infotype 1007 - this closes the requisition in SF.

I would have thought that if we simply set the vacancy as open again in SAP (infotype 1007 again) for the same from/to dates that this would automatically re-open the form - however, it is creating a brand new requisition in SF every time.

Is this normal behaviour, or am I doing something wrong?

As integration is turned on, the "Reopen Requisition" button in PPOME is greyed out for the filled vacancy..

Thanks in advance.

Sean