We are having problem with your plugin.
We tried to populate with a Custom Post Type as you can see in the screenshot which is attached.
The result we got was the set of Ids stored in drop down values instead of the actual titles.
Could you please help us in getting the title instead of the ids?
Please go through the below provided link,
http://18.104.22.168/gravityformissue/gformissue.pdf, to see the screenshots to better understand the situation.