Hmm, I just tried with some text copied from here
https://sangham.net/km/tipitaka/sut/kn/uda/sut.kn.uda.40, which was included as a text from here
https://sangham.net/km/tipitaka/book_052.
At first I did not find any results. But after visiting the "original" page
https://sangham.net/km/tipitaka/book_052 from where the text was included, and then searching again, the text was found.
So it seems there is missing a lot in the index. Maybe something got lost or invalid by the upgrade.
Normally, whenever opening a page, or editing it in the DokuWiki, it is indexed. If changing files directly on the server, by FTP upload, this is not updated in the index. Maybe same with using BatchEdit, not sure.
There is a plugin that can be used to rebuild the whole DokuWiki index, but as tried out in the past, it takes extremely long to finish for a huge Wiki as this, and one has to leave the browser open all the time.
Not sure if I should clear and rebuild the whole index, or just update it.
I will first take a closer look at how it actually works.