3673214 - Error "Adding items manually is not allowed in SDF" when editing SD2 document

When trying to do a change (e.g. setting a rejection reason) on a sales order without charge, of type SD2, created from a returns order, the error "Adding items manually is not allowed in SDF" (Message no. CX_MSR_TRC095) shows.

SAP S/4HANA Cloud Public Edition

1. Create a returns order using the app 'Manage customer returns'. 
2. Select the replacement as the refund type.
3. Create replacement order,  and during the creation, change the material and save.
4. Go to change mode and try to make any change in the document.
5. The error is issued.

The material was manually changed on the SDF order during creation. This is not allowed on ARM, so the error message is correctly issued.

Since the order is no longer supported on ARM, the process shouldn't continue. The order should be deleted and a new one should be created, following the original material on the returns.

SDF, SD2, sales order without charge, returns order, returns overview, refund type, subsequent delivery free of charge, ARM, advanced returns management, CX_MSR_TRC095 , KBA , LO-ARM-SD-2CL , Sales (Public Cloud) , Problem