I had a functioning database on xampp mw1.27.4 and no search-problems.
I exported it with mysqldump and imported it into an empty online.database. Then i installed mw1.27.4 and connected to the database and it was imported and everything functioned with the exception of the search-function, which has an error (and then normally goes to a site in which it offers to create a site with this title).
I made the same with mw1.29 and had a similar problem. (Details at http://127.spiritwiki.de/ and at http://w129.mb-info.eu ) -> search anything in the database - only sometimes it finds if it is in the database. I have no php -cli - mode and can only update with 'php maintenance/update.php --skip-external-dependencies' : The error is ../OutputPage.php: Class 'OOUI\MediaWikiTheme' not found.
A normal installation on an empty database does not have these problems.
I have switched the error-functions on as You can see. (Please only creative commentaries).