Message type: E = Error
Message class:  SD_FREE_GOODS_MSG - Message class for Free Goods maintenance 
Message number: 039
Message text: Unit conversion error.
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The SAP error message SD_FREE_GOODS_MSG039 typically indicates a unit conversion error related to free goods in the Sales and Distribution (SD) module. This error can occur when there is a mismatch in the units of measure (UoM) between the free goods and the main product during sales order processing.
Cause: Unit of Measure Mismatch: The free goods are defined in a different unit of measure than the main product. For example, if the main product is sold in pieces (EA) and the free goods are defined in boxes (BX), the system may not be able to convert between these units correctly.
Configuration Issues: There may be issues in the configuration of the free goods determination procedure or the unit of measure settings in the material master. Missing Conversion Factors: The conversion factors between the units of measure may not be defined in the system, leading to the inability to convert quantities correctly. Incorrect Sales Order
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