A gateway instance from previous BusinessConnect domain is getting added by default to new BC domain after importing the csx file. The GS instance is not defined new domain. 

On trying to remove that instance, one gets the below error :
<<<<<<<
Failed to retrieve RMIServer stub: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: xxx.yyy.com; nested exception is: 
   java.net.ConnectException: Connection refused (Connection refused)]: Failed to retrieve RMIServer stub: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: xxx.yyy.com; nested exception is: 
   java.net.ConnectException: Connection refused (Connection refused)]
>>>>>>>

One can even see the GS instance connecting to the interior server but failing.

Linux environment

You must follow the following steps in order to delete the problematic instance :
1. Make sure the problematic instance is not running in the old domain (kill instance) before trying to delete it
2. Delete the instance from BC_SCHEDULED_TASK table after taking a backup of the table row
3. Restart Administrator and the instance should be deleted

BC_SCHEDULED_TASK table is the only place where a reference to the Gateway instance is stored in the database.

If this does not help, perform the following steps :
1. Stop the Business Connect engines
2. Un-deploy and delete the Business Connect application
3. Re-initialize the database
4. Re-create the BusinessConnect deployment and the problematic GS instance will be deleted
 

A Gateway instance from an old BusinessConnect environment showing up in new BusinessConnect environment in Administrator after import

Gateway instance, RMIServer, BC_SCHEDULED_TASK