Hi Prateek,
This could be due to the processing of same Account number by two different consequent IDOCs.
One suggestion could be just try and check changing the output mode from "Collect IDocs" to "Transfer IDoc Immed." in the Partner Profile setting in the sending side.
Also, similarly check whether "Trigger Immediately" is selected on the receiving side in the Partner Profile.
Because "Collect IDocs" or "Trigger by background program" will try to process both the IDOC's at the same time involving same Account number, resulting in interlocking.