Hi Abdul,
Please compare the BUPA_MAIN Bdoc (extended data segments) between request download Vs. delta download for the same customerID. If a particular value is missing between them, you can take debug help to trace back using ECC data exchange FM or check if that value is maintained properly in customer master data in ECC.
Also, can you show all the error messages in the errorsegments window, if they exist.
Thanks
Barun