Leo! You are right! This error was caused by plugin. I’ve checked that, this is an issue generated by Generate Press Plugin.
When I’m trying to search something in WordPress by default (without Generate Press plugin) all results are in descending order, but when I enable Generate Press plugin, and I’m trying to search something, at first articles appear tagged with the same tag as the search result, and then articles appear that contain the word you’re looking for. That’s the problem.
So we have situation where we have descending order news by tag and date, and after all those news we have an articles contains searched string without tag. This causes situations where the dates are mixed up. Search query is modified and it’s not god as default WordPress default. How can I change this search query to WordPress default.