Hi,
I cannot imagine duplicate records in a Standard DSO with ID as Key field. The record will for sure be overwritten. The Key Figures will be updated according to the Transformation setting: overwrite or summation.
I suspect that you might have a Write-optimized DSO. Here you can optionally define a Semantic Key. However, the "real" Key fields are Request ID, Data Package and Record. Here you can have "duplicate" records for the same Semantic Key.
If you have a Write-optimized DSO, then I suggest to change it to a Standard DSO.
Best regards,
Sander