diff --git a/src/pretix/base/migrations/0302_resolve_duplicate_codes_and_secrets.py b/src/pretix/base/migrations/0302_resolve_duplicate_codes_and_secrets.py
new file mode 100644
index 0000000000..01b1cfdebb
--- /dev/null
+++ b/src/pretix/base/migrations/0302_resolve_duplicate_codes_and_secrets.py
@@ -0,0 +1,58 @@
+# Generated by Django 4.2.8 on 2024-07-01 09:27
+import logging
+
+from django.db import migrations
+from django.db.models import Count
+
+logger = logging.getLogger(__name__)
+
+
+def clean_duplicate_secrets(apps, schema_editor):
+    # This will autofix all possible duplicate Order.code and OrderPosition.secret values,
+    # unless Order.code is already too long to append something. This would need to be fixed by
+    # sysadmins manually.
+    OrderPosition = apps.get_model("pretixbase", "OrderPosition")
+    Order = apps.get_model("pretixbase", "Order")
+
+    qs = OrderPosition.all.values("secret", "order__event__organizer_id").order_by().annotate(c=Count("*")).filter(c__gt=1)
+    for row in qs:
+        affected = OrderPosition.all.filter(
+            **{k: v for k, v in row.items() if k != "c"}
+        ).order_by("pk")
+        logger.error(f"Found {row['c']} tickets with with the same secret \"{row["secret"]}\" in organizer {row['order__event__organizer_id']}, all except one will be changed")
+        for i, a in enumerate(affected):
+            if i > 0:
+                a.secret = a.secret + "__dupl__" + str(a.pk)
+                logger.info(
+                    f"Ticket {a.pk} has new secret {a.secret}"
+                )
+            a.save(update_fields=["organizer_id", "secret"])
+
+    qs = Order.objects.values("code", "event__organizer_id").order_by().annotate(c=Count("*")).filter(c__gt=1)
+    for row in qs:
+        affected = Order.objects.filter(
+            **{k: v for k, v in row.items() if k != "c"}
+        ).order_by("pk")
+        logger.error(f"Found {row['c']} orders with with the same code \"{row["code"]}\" in organizer {row['event__organizer_id']}, all except one will be changed")
+        for i, a in enumerate(affected):
+            if i > 0:
+                if len(a.code) > 16 - len(str(a.pk)):
+                    raise ValueError(f"Cannot auto-fix order with duplicate code {a.code}, order code is too long already")
+                a.code = a.code + str(a.pk).zfill(16 - len(a.code))
+                logger.info(
+                    f"Order {a.pk} has new code {a.code}"
+                )
+            a.save(update_fields=["organizer_id", "code"])
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        (
+            "pretixbase",
+            "0301_reusablemedium_remove_orderposition",
+        ),
+    ]
+
+    operations = [
+        migrations.RunPython(clean_duplicate_secrets, migrations.RunPython.noop),
+    ]
diff --git a/src/pretix/base/migrations/0269_alter_order_organizer_alter_orderposition_organizer.py b/src/pretix/base/migrations/0303_alter_order_organizer_alter_orderposition_organizer.py
similarity index 68%
rename from src/pretix/base/migrations/0269_alter_order_organizer_alter_orderposition_organizer.py
rename to src/pretix/base/migrations/0303_alter_order_organizer_alter_orderposition_organizer.py
index a96ee2de93..237c5e7a52 100644
--- a/src/pretix/base/migrations/0269_alter_order_organizer_alter_orderposition_organizer.py
+++ b/src/pretix/base/migrations/0303_alter_order_organizer_alter_orderposition_organizer.py
@@ -1,15 +1,14 @@
 # Generated by Django 4.2.8 on 2024-07-01 09:27
 
-from django.db import migrations, models
 import django.db.models.deletion
+from django.db import migrations, models
 
 
 class Migration(migrations.Migration):
-
     dependencies = [
         (
             "pretixbase",
-            "0268_remove_subevent_items_remove_subevent_variations_and_more",
+            "0302_resolve_duplicate_codes_and_secrets",
         ),
     ]
 
@@ -17,21 +16,12 @@ class Migration(migrations.Migration):
         migrations.RunSQL(
             "UPDATE pretixbase_order "
             "SET organizer_id = (SELECT e.organizer_id FROM pretixbase_event e WHERE e.id = pretixbase_order.event_id) "
-            "WHERE pretixbase_order.id IN (SELECT id FROM pretixbase_order o2 WHERE o2.organizer_id IS NULL);"
+            "WHERE pretixbase_order.organizer_id IS NULL;"
         ),
         migrations.RunSQL(
             "UPDATE pretixbase_orderposition "
             "SET organizer_id = (SELECT e.organizer_id FROM pretixbase_order o LEFT JOIN pretixbase_event e ON e.id = o.event_id WHERE o.id = pretixbase_orderposition.order_id) "
-            "WHERE pretixbase_orderposition.id IN (SELECT id FROM pretixbase_orderposition op2 WHERE op2.organizer_id IS NULL);"
-        ),
-        migrations.AlterField(
-            model_name="order",
-            name="organizer",
-            field=models.ForeignKey(
-                on_delete=django.db.models.deletion.CASCADE,
-                related_name="orders",
-                to="pretixbase.organizer",
-            ),
+            "WHERE pretixbase_orderposition.organizer_id IS NULL;"
         ),
         migrations.AlterField(
             model_name="order",