When you search, and there are enough results for it to be paginated, the pagination links don't include the query string.
For instance, try to search for "git" and click on page 2. The link is now search?page=2, which redirects to /lessons. It should instead be search?q=git&page=2
I see what the confusion is. The OP is referring to site wide search (hit 's' on your keyboard). And that is not working with pagination. The working links provided in this post so far are forum search results which are in fact working.