Thanks for sharing back what solved it for you, @Gaston_De_Larrechea! Adding some other advice from a teammate of mine on this topic from another support conversation, in case useful to others who find this
It looks like you're using an unknown variable, my_OID, in your updateMapping_test query that's not defined anywhere. Since you're trying to pass my_OID_Keyto your query using additionalScope, you'll need to use my_OID_Key in your updateMapping_test query and not my_OID. The keys you're passing in additionalScope needs to match in your query.
To understand more about additionalScope, I recommend following our docs on Running a JS query for each row in a table, or this community thread.