People Result Sorting Issue in SharePoint 2013

We are trying to sort people result so the when users search for a user name, for example John, we should see the result sorted by last name in ascending order: John A John B John C ....etc

So in a development box (single SP 2013 server) we did the following: 1. Edited LastName managed property (in search schema) and activated the box Sortable as shown below:

We crawled the content database, and then we created a result source based on Local People Results and under sorting tab we selected LastName managed property and the sort order ascending as shown below:

these steps worked perfectly in the development environment, but it did not work in the production one, and the only difference is that the current production has content sources that would take weeks to do a full crawl (those content sources to crawl other SharePoint farms) and the only full crawl I did on production was for local content and that is including mysites (http and sps3 protocols) and I think that should be it since the crawled propeties mapped to LastName are People:LastName, People:SPS-PhoneticLastName I could be wrong though...I have tried a full user profile import and did full crawl for local contents to no avail...I am lost and I don't know what else to do.