The cause of the problem has been identified: commands were sent using the wrong spacecraft ID (34 instead of 35). This was clearly recognised by specialists and confirmed by the telemetry analysis performed following the problem.
ATV systems behaved perfectly until the interruption, and it is ready to repeat an undocking attempt. Due to operational constraints, NASA has requested to wait until Thursday, 27 September. If this date is confirmed, the separation time will be at 21:00:01 GMT.
As an additional consequence of this postponement, reentry will be postponed to at least 2 October, due to the end of validity of the current NOTAM and the 6-day minimum notice for issuing a new one.