diff --git a/public_html/assets/api/install.php b/public_html/assets/api/install.php
index 228306c..9087f0f 100644
--- a/public_html/assets/api/install.php
+++ b/public_html/assets/api/install.php
@@ -100,10 +100,24 @@ trait InstallAPI {
                 NOW()                                     AS iw_created_at
             FROM tbl_customer c
             WHERE c.c_uid = '{$c_uid}'
+                AND NOT EXISTS (
+                    SELECT 1
+                    FROM tbl_install_waitlist iw
+                    WHERE iw.iw_customer_uid = c.c_uid
+                    AND iw.iw_status NOT IN ('DELETED','COMPLETED')
+                )
         ";
 
         qry($sql);
 
+        if (mysqli_affected_rows($GLOBALS['conn']) == 0) {
+            echo $this->json([
+                'ok' => 0,
+                'msg' => '이미 waitlist에 존재합니다.'
+            ]);
+            return;
+        }
+
         $iw_uid = mysqli_insert_id($GLOBALS['conn']); // or global db handle
 
         echo $this->json([
diff --git a/public_html/doc/install_wait_list.php b/public_html/doc/install_wait_list.php
index ace2890..8432175 100644
--- a/public_html/doc/install_wait_list.php
+++ b/public_html/doc/install_wait_list.php
@@ -2128,8 +2128,8 @@ while ($row = mysqli_fetch_assoc($rmem)) {
     unassignDailyInstall(ids);
   });
 </script>
-<script src="/js/install_wait_modal.js?v=20260204"></script>
-<script src="/js/customer_image.js?v=20260204"></script>
+<script src="/js/install_wait_modal.js?v=<?=time()?>"></script>
+<script src="/js/customer_image.js?v=<?=time()?>"></script>
 
 <!-- add modal -->
 <div class="modal fade" id="addInstallWaitModal" tabindex="-1" aria-hidden="true">