diff --git a/templates/admin/monitor.html b/templates/admin/monitor.html
index 388511e..6f3756c 100644
--- a/templates/admin/monitor.html
+++ b/templates/admin/monitor.html
@@ -452,6 +452,11 @@ async function stopSelectedDevices(){
   setTimeout(loadMonitor,500);
 }
 
+// ================== 设备画面查看 ==================
+let _shotTimer=null;       // 自动刷新定时器
+let _shotSerial='';        // 当前查看的 serial
+let _shotLoading=false;    // 防止并发请求
+
 // 打开截图弹窗
 function openScreenshot(serial){
   _shotSerial=serial;
@@ -493,7 +498,8 @@ function startShotTimer(){
   _shotTimer=setInterval(refreshShot,3000);
 }
 function stopShotTimer(){
-  if(_shotTimer){clearInterval(_shotTimer);_shotTimer=null;}
+  // 用 typeof 容错：变量未声明时不报错（避免 closeModal 调用时抛异常导致弹窗关不掉）
+  if(typeof _shotTimer!=='undefined'&&_shotTimer){clearInterval(_shotTimer);_shotTimer=null;}
 }
 
 // 取一次截图
@@ -1311,13 +1317,16 @@ function showModal(){
   document.getElementById('modal-overlay').classList.add('show');
 }
 function closeModal(){
-  // 清理截图弹窗的自动刷新定时器（避免关闭后后台继续请求）
-  stopShotTimer();
-  _shotSerial='';
-  // 还原弹窗样式（截图弹窗会加 shot-modal，关闭时移除）
-  const box=document.getElementById('modal-box');
-  if(box)box.classList.remove('shot-modal');
-  document.getElementById('modal-overlay').classList.remove('show');
+  // 先关闭弹窗（最重要的一步，确保一定执行）
+  const ov=document.getElementById('modal-overlay');
+  if(ov)ov.classList.remove('show');
+  // 再做清理工作，任何异常都不影响弹窗关闭
+  try{
+    stopShotTimer();
+    _shotSerial='';
+    const box=document.getElementById('modal-box');
+    if(box)box.classList.remove('shot-modal');
+  }catch(e){console.warn('closeModal cleanup error:',e);}
 }
 
 // ================== 行内按钮操作（停止/执行/启停等，自动 toast + 刷新）==================
diff --git a/web_server.py b/web_server.py
index 0a9570d..069e756 100644
--- a/web_server.py
+++ b/web_server.py
@@ -15,7 +15,7 @@
 import os
 import time
 
-from flask import Flask, jsonify, request, redirect, url_for, render_template, Response
+from flask import Flask, jsonify, request, redirect, url_for, render_template, Response, make_response
 from flask_login import (LoginManager, login_user, logout_user,
                          login_required, current_user)
 
@@ -55,7 +55,10 @@ def load_user(user_id):
 @login_required
 def index():
     """单页应用首页。"""
-    return render_template("admin/monitor.html")
+    resp = make_response(render_template("admin/monitor.html"))
+    resp.headers["Cache-Control"] = "no-store, no-cache, must-revalidate, max-age=0"
+    resp.headers["Pragma"] = "no-cache"
+    return resp
 
 
 @app.route("/login", methods=["GET", "POST"])