Seems there's a issue when dealing with the Robots.txt, where the URL: [domain]/ajaxfiltersprosearch/search
Is searched which, for us, leads to an error. While the error is likely on our part. I feel that the Robots.txt generated by Nopcommerce should be amended by plugins such as the Ajax Filter Pro to exclude URLs.
Yes, we will think about modifying the Robots.txt from our plugins.
At the moment you can manually add the route to the robots.txt file.
Thanks for your feedback !