If you do an second full load, the query from the source qualifier is getting records from W_PRODUCT_D, but this table is not truncated yet at this stage. There is a lookup trying to transform created_by_wid from W_USER_D, which holds the new values, but W_PRODUCT_D has a created_by_wid from the previous ETL. Hence no value is found. If you truncate the table W_PRODUCT_D, you can restart the DAC and all should complete fine.
Hope this helps,