Problem after changing permalinks

Hi,

I changed permalinks from /category/post-name/ to /post-name/ and on the end of every link is now the same number: ?zsid=173157858cb22a9

For example:

https://www.vikingmarketing.si/storitve/?zsid=173157858cb22a9
https://www.vikingmarketing.si/o-nas/?zsid=173157858cb22a9
https://www.vikingmarketing.si/blog/?zsid=173157858cb22a9

When I activate and deactive some plugins I get this message:
Warning: Cannot modify header information – headers already sent by (output started at /home/viking/public_html/wp-config.php:95) in?/home/viking/public_html/wp-includes/pluggable.php?on line?896

Can you help me?