Search function: "No posts exist inside this topic for the selected time frame."

[Bikey]

Regullary I have that the Forum search function does not work properly.
After entering the search is often not possible to open many of the articles that have been found. If you click the link to go to the article, a page appears: "No posts exist inside this topic for the selected time frame."

Example: search for "global variables" none of the articles are found.

No difference when using different browsers.