404 error on searches

I am getting this error message:

404
The above error was returned by your server, for more details please consult your servers error logs.

In the debug.log I see:

PHP Warning: preg_replace(): Unknown modifier ‘/’ in /home/caelch5/basketsofafrica.com/boa-stg-june-202/wp-content/plugins/string-locator/includes/class-search.php on line 425

????