Correct Mike. We verified the data source is same for all duplicates. Also as I said same video is displaying twice in the right rail on the page.

If we look at the ItemID assigned, those are repeating after five and we see duplicate items on the page as well.

Aah ok that is the catch. In that case I agree with Chris that creating a package of just Content Item, Media Items and Templates should work. But you might face issues with digital marketing related stuff etc. I would keep this answer here for others who are looking for similar upgrade option for source Sitecore version below 8.1.

Thanks Tyler but my question is different. Yes I installed using SIF but OOTB CM/CD/PRC/REP doesn't have separate connection string for Collection Search. What all you have is just Collection, Marketing Automation, Marketing Reporting and xDB Reference Data. I want to add a new connection string dedicated for Collection Search to scale out.