Hi,
If you are using MATP may be ATP tree strcture is getting converted in to PPDS Planned orders automaticaly on saving sales order. During conversion of ATP tree strcture to PPDS Planned order scheduling strategy is used from PPDS global parameters. Hope you have tried by changing scheduling strategy for ATP to PPDS conversion and used offset in strategy. Also try to change scheduling direction from backward+reverse to forward+reverse. Refer to OSS note 480292 for details.
I think this will work.
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