Are you loading the data via S3? If your trying to do an import, I have found it can break if there’s an extra space in the field. I would double check the field. 

If you’re not loading the data via S3, you can export both records and use Excel to see if the fields match directly. Sometimes there are bad characters in the field. 

HI JEAN,

Thanks for your suggestion.

In the rule we are performing an action- load to relationship in which the rule is failing partially with one or two  error records.

We are fetching the data from account and customer hierarchy object and merging it and on merge we are performing transformation.

So on loading to relationship on final transformation, we see there are 2 or 1 error records with invalid account coming.

I am eager to know what can the real reason behind this can be?

Can anyone help me with this?

I think you would be best to contact support. Someone will need to look at the data and your rule to help you. Providing help for a data issue like this is quite difficult without getting access to your instance and looking through it all.