Sharepoint Search Query does not retrieve all the search results

Good Day, 

Currently I am having an issue whereby my SharePoint Search Query only retrieves a few documents. For eg. whenever I submit this query it will only return me Simple1.xml and Query1.xml. But not Simple2.xml and Query2.xml both the files contains almost the same values as Simple1.xml and Query1.xml with the keyword "document" in them. Please do assist thank you!

I have the following configurations in placed from this guide. But it does not work.

https://learn.microsoft.com/en-us/sharepoint/troubleshoot/search/search-results-missing?source=recommendations

I found this but I can't seem to replicate the steps as I am using the latest sharepoint.
https://www.aquaforest.com/blog/finding-duplicate-files-in-sharepoint