SAP Message V1336 - Item &1 already has a schedule line for date &2 &3 &4

Diagnosis
A schedule line with the same date and the same time was alreadycreated for item &V1&.

System Response
You receive a warning message because this does not usually happen.

Procedure
Check whether you really want to create more than one schedule line fordate &V2& &V3& and time &V4&.

207838ATP check terminates with error message V1336
641959CRM-transfer in R/3: Schedule line error during the change