Difference Stage in PX

[soracev]

I am using a Difference Stage in one of my jobs to compare data from 2 input datasets. Both datasets have 3 Key Columns (with same names) and all other columns I want to treat as Value Columns (in order to compare the values in them from both datasets). The value columns have also same names in both datasets (as mentioned in the DS help files).
When I run the job, everything executes well, but I am getting warnings for every single field with the following description:
"When checking operator: Dropping component "Column_Name" because of a prior component with the same name".
Could anybody please let me know what am I doing wrong?

Thanks