Filter does not filter projects

Symptom

Clicking a filter item reloads the same items, or the page jumps.

Cause

• Category slugs with non-Latin characters, which the server encodes differently from the way the filter sends them.
• Permalinks that include /index.php/.
• A page cache or a firewall that strips or blocks the AJAX request.
• A JavaScript error from another plugin on the same page.

These are category slugs that will not work:

Fix

1. Give every category a Latin slug. Open Visual Portfolio → Categories, edit the category and replace the slug; the name stays as it is.
2. Open Settings → Permalinks and choose a structure without index.php.
3. Exclude the page from your page cache, or allow POST requests to it in your firewall.
4. Open the browser console on the page and look for JavaScript errors from other plugins.