You are doing a number of unusual things regarding geo-filtering and redirects that may be involved. I had to use a VPN to access your site.
However you can see the _fs querystring params directly in your nav links.
If you did not add them there intentionlly, then it’s likely they were added by scripts. Two primary suspects here. Funnelytics is the most likely culprit, but Google Optimize could be involved as well.