This behavior is quite odd.  I execute a search, 8 items are returned.  However, when I use the refiners, additional search results are displayed (NOT a subset of an un-refined search).

I did some troubleshooting using the SharePoint 2013 Search Query tool and found the same behavior until I turned off "Trim Duplicates".  SharePoint mistakenly thinks these documents are duplicates (same titles).

In the search results page, how do I turn off "Trim Duplicates", I don't see that option on the Search Results Web Part or in the custom Result Source I am using.

The only thing I've found online is to export the web part and modify the 'TrimDuplicates' setting and re-upload it.

Hi,

According to your post, my understanding is that you wanted to disable the Trim Duplicates in SharePoint 2013.

In SharePoint 2013, the Remove Duplicate Results option has been removed, but we can use the View Duplicates Link option.

The TrimDuplicates to specify whether to trim away the duplicate search results from the result set. TrimDuplicates is true by default.

If you want to disable the feature, as you had said, we should export the web part and modify the 'TrimDuplicates' setting then re-upload it.

http://blogs.perficient.com/microsoft/2013/04/sharepoint-2013-search-not-display-all-results/

Thanks & Regards,