<ul><li>Fixed <code>tour/table.php</code>: wrapped <code>&lt;th&gt;</code> elements in <code>&lt;tr&gt;</code> inside <code>&lt;thead&gt;</code> — missing wrapper caused DataTables to miscount columns → <em>"Requested unknown parameter '5' for row 36"</em></li><li>Fixed <code>tour/steps_table.php</code>: same missing <code>&lt;tr&gt;</code> in <code>&lt;thead&gt;</code> (6 columns, error on column index 5)</li><li>Fixed <code>checklist/table.php</code>: same missing <code>&lt;tr&gt;</code> in <code>&lt;thead&gt;</code></li><li>Fixed <code>checklist/items_table.php</code>: same missing <code>&lt;tr&gt;</code> in <code>&lt;thead&gt;</code></li><li>Root cause: DataTables TN/4 error — <code>&lt;th&gt;</code> directly inside <code>&lt;thead&gt;</code> without <code>&lt;tr&gt;</code> wrapper is invalid HTML; DataTables cannot reliably determine column count, producing column index out-of-bounds on row access</li></ul>