Thank you! That seem to do the trick. In my HL7 router, just below bad message handler I added the Business Service in Response from and new operation in  ResponseTargetConfigNames.

In addition in order to route the Nacks, I changed the Reply Code Action from default to :?R=RF,:?E=W,:~=S,:?A=C,:*=S,:I?=W,:T?=C in my original operation.

Additional documentation can be found at:

https://docs.intersystems.com/healthconnectlatest/csp/docbook/Doc.View.cls?KEY=EHL72_settings_bo#EHL72_ReplyCodeActions

https://docs.intersystems.com/healthconnectlatest/csp/docbook/Doc.View.cls?KEY=EHL72_settings_bo#EHL72_GetReply  

https://docs.intersystems.com/healthconnectlatest/csp/docbook/DocBook.UI.Page.cls?KEY=EHL72_scenarios

Thanks again!