Aggrigator Stage giving worng result

[prasson_ibm]

Hi,
I am using aggrigator stage in my job.job design is like this:-

dataset---->aggrigator stage----->db2 stage
I want sum of one column basced on five key columns.Column which i m using for sum is decimal(10,5) and i want o/p also as decimal(10,5).Some of aggrigated output are NULL but source has not null records.If you have any idea why i m getting this issue,please let me know

Thanks in advance.