Hey @Jack_T,
By ip/url, I was referring to the url of GET/POST requests in the queries, not the url of the app itself.
It seems as if queries are global variables shared across apps. So, when I duplicate an app, the original and the duplicated app are both sharing global queries. Changing the url of a query changes it in both apps simultaneously, so it is not possible to host the backend of the two apps on two different servers.
For now, I just found a simple workaround by manually recreating new queries in the duplicate app with the same parameters (except the url) as the older queries.
Thanks.