Hi,
I have run a quick debugging on the executed query for the search term ‘agfa’, and it returns 194 results, that should be 19 pages, not 10, however it prints only 10.
Then I checked if the posts per page values are set correctly, but everything seems to be okay.
If I manually navigate to page 19, the last of the results work, so that means, that the navigation is not working correctly. See this: https://i.imgur.com/J0zWhM7.png
I checked, but the correct results count & page count is passed to the search query, so I am guessing that the navigation might use a different method to calculate the page count. The maximum page count should be queried from the $wp_query->max_num_pages variable.
I suggest investigating the navigation script, to make sure it uses this variable correctly.