I ran into 3 different sharepoint 2019 (on-premise) search result quirks that I'm not sure if it's by design or configuration issue.
The first scenario:
From the "Home" site (sub-site or site collection)'s search box on top left, the search term would show couple files, but when we click on show more result, it will not return any result. However, if user change from the actual site to "All Site," the result would show.
The second scenario:
The third scenario:
From a different document library at the same site, it would show no match, but you can actually see the file there. I can also confirm the file shows up in the Crawl Log in the central admin. The document library settings also has the library to appear in the search result.
I've been researching this for a few days already without too much luck. I've done re-indexes, re-built the search service. Open up the firewall 808 port in Server 2019. Any pointer will be much appreciated!