Hi again, apologies I overlooked your update.
OK, so I have asked the team for some input, and we’re thinking that you maybe need to check into the different setups for replication to make sure you are setting up correctly. It’s important to get it right, it can take time to unpick and more importantly you don’t want to compromise your database. Specifically, the error is highlighting that you already set up the slave database, so you don’t need to do it again during processing.
So while you might be able to ignore the error and just continue, it’s important to understand why you have it in the first place, so that you don’t get trouble later on. It seems like you are wanting to achieve a MASTER <-> (MASTER+SLAVE) set up.
So, I have found some resources for you to check through first, so that you can make sure of the model of replication that you would like to achieve:
free ebook: https://www.percona.com/resources/mysql-ebooks/mysql-replication
https://www.percona.com/resources/webinars/mysql-replication-troubleshooting - this one in particular might highlight whether you have the right strategy in place by looking at how to fix things that are not right
[/LIST] Please check those out, then if you still have questions feel free to ask again. Thanks!