When I double-click on Treasure Hunt to build it, I sometimes get whatever is first in my favorites list. It may be a colony ship or a constructor/erector. I have recently designed a better scout ship that is now first in my favorites list. It is the one that is now sometimes put into the build queue instead of Treasure Hunt. I have learned to always look at the build queue to see what was actually put into it so I can make the change then instead of finding out after the build is complete.
I submitted Ticket: #WDR-548-12738 about this problem in early August and just updated it.