I tried your configuration suggestions and still have the same issues. I have even set stop words and no effect.
https://imgur.com/a/ZDAhGfA
https://imgur.com/Wtf8JHQ
When I try searching for “на силата” it matches correctly the pages where these exact words are. But if these exact words are not present as a text in certain page, it matches the first double letter word only, as shown in the picture.
Maybe it does not work with Cyrillic fonts only?