Chaitanya,
.
Check if there are any dumps in ECC using st22 transaction.
Can you check if the RFC user which has SAP_ALL access to connect to ECC system.
Also can you compare the authorization of the users on Client 210 and 220 and try to find the missing authorization.
Can you let me know the Data transfer method which you are using under Datastore>Advanced settings.
Make sure you set the ABAP Execution Method to Generate and Execute and Execute in Background to Yes
Regards
Arun Sasi