This is happening to me as well. I update the map and try to push to private island. I keep getting the same island code I had previously and no updates is made. I even make a note for the version which is then not updated.
UPDATE: I would have left a reply but the thread was closed shortly after I posted for some reason…
I tried inserting the map code on a different XBOX console for testing and it loaded the correct version. Then I restarted Fortnite on the other console I was testing with and it worked.
If you are having this issue, try restarting Fortnite and pulling the map back up. I guess it was cached???