Not sure if it’s related to my setup or the plugin or a WordPress update with changes to WP_Query but the s argument passed empty to WP_Query is causing the issue.
I created a function to hook to your WP_Query filter and that solves it:
function post_grid_filter_query_args($default_query = null) {
unset($default_query['s']);
return $default_query;
}
add_filter('post_grid_filter_query_args', 'post_grid_filter_query_args', 10, 1);
Glad to see you solved it.
Can you please check which plugin or theme causing the issue so we can update plugin to fix the issue.
Regards