Using native format to bulk copy data into an improperly defined table can cause the table to be loaded incorrectly. The incorrect loading may appear as an unusual formatting of data in the target table. This also applies to client tools that use the bcp API in native mode.
Native format is intended for high-speed data transfer between identically defined Microsoft® SQL Server™ tables. To achieve the optimum transfer rate, few checks are performed regarding data formatting. If the table is not defined correctly, use character format.
Correct table definition includes the correct number of columns, data type, length, and NULL status.