diff --git a/app/app/dashboard/views/setting.py b/app/app/dashboard/views/setting.py
index 3b140b8..f0de91a 100644
--- a/app/app/dashboard/views/setting.py
+++ b/app/app/dashboard/views/setting.py
@@ -174,7 +174,12 @@ def setting():
             flash("Your preference has been updated", "success")
             return redirect(url_for("dashboard.setting"))
         elif request.form.get("form-name") == "random-alias-suffix":
-            scheme = int(request.form.get("random-alias-suffix-generator"))
+            try:
+                scheme = int(request.form.get("random-alias-suffix-generator"))
+            except ValueError:
+                flash("Invalid value", "error")
+                return redirect(url_for("dashboard.setting"))
+
             if AliasSuffixEnum.has_value(scheme):
                 current_user.random_alias_suffix = scheme
                 Session.commit()
diff --git a/app/crontab.yml b/app/crontab.yml
index 1198d54..416e13b 100644
--- a/app/crontab.yml
+++ b/app/crontab.yml
@@ -14,8 +14,9 @@ jobs:
   - name: SimpleLogin Custom Domain check
     command: python /code/cron.py -j check_custom_domain
     shell: /bin/bash
-    schedule: "15 2 * * *"
+    schedule: "15 */4 * * *"
     captureStderr: true
+    concurrencyPolicy: Forbid
     onFailure:
       retry:
         maximumRetries: 10
@@ -26,7 +27,7 @@ jobs:
   - name: SimpleLogin HIBP check
     command: python /code/cron.py -j check_hibp
     shell: /bin/bash
-    schedule: "16 */4 * * *"
+    schedule: "*/5 * * * *"
     captureStderr: true
     concurrencyPolicy: Forbid
     onFailure: