diff --git a/static/index.html b/static/index.html
index affd517c..9e01d814 100644
--- a/static/index.html
+++ b/static/index.html
@@ -214,7 +214,7 @@ document.addEventListener('DOMContentLoaded', function() {
         if (he) delete he.dataset.rendered;
       }
       if (name === 'health' && !healthRefreshInterval) {
-        healthRefreshInterval = setInterval(refreshHealth, 10000);
+        if (!healthRefreshInterval) healthRefreshInterval = setInterval(refreshHealth, 10000);
       }
       document.querySelectorAll('.tab-content').forEach(el => el.classList.add('hidden'));
       document.querySelectorAll('.tab-btn').forEach(el => el.classList.remove('active'));
@@ -616,9 +616,12 @@ function renderMarket() {
 
 // ── Evaluation Tab ──
 let evalTimer = null;
+let evalBusy = false;
 function renderEvaluation() {
+  if (evalBusy) return;
+  evalBusy = true;
   const el = document.getElementById('tab-evaluation');
-  if (evalTimer) clearInterval(evalTimer);
+  if (evalTimer) { clearInterval(evalTimer); evalTimer = null; }
   fetchJSON('/api/tracking').then(data => {
     const tracks = data.tracks || [];
     const stats = data.stats || {};
@@ -709,8 +712,9 @@ function renderEvaluation() {
           }).join('')}</tbody>
         </table>
       </div>`;
-    evalTimer = setInterval(renderEvaluation, 30000);
-  });
+    if (!evalTimer) evalTimer = setInterval(renderEvaluation, 30000);
+    evalBusy = false;
+  }).catch(() => { evalBusy = false; });
 }
 function triggerEval() {
   const btn = document.querySelector('#tab-evaluation button');
@@ -797,8 +801,9 @@ async function openStock(code) {
   const chartCanvas = document.getElementById('modalChart');
   chartCanvas.innerHTML = '<canvas id="stockChart"></canvas>';
   const ctx = document.getElementById('stockChart').getContext('2d');
+  if (window._stockChart) { try { window._stockChart.destroy(); } catch(e) {} window._stockChart = null; }
   if (stockData.price_history && stockData.price_history.length > 1) {
-    new Chart(ctx, {
+    window._stockChart = new Chart(ctx, {
       type: 'line',
       data: {
         labels: stockData.price_history.map(p => p.date),