Fix secret regeneration

src/pretix/base/services/orders.py

@@ -2425,8 +2425,8 @@ class OrderChangeManager:
             elif isinstance(op, self.SplitOperation):
                 split_positions.append(op.position)
             elif isinstance(op, self.RegenerateSecretOperation):
-                op.web_secret = generate_secret()
-                op.save(update_fields=["web_secret"])
+                op.position.web_secret = generate_secret()
+                op.position.save(update_fields=["web_secret"])
                 assign_ticket_secret(
                     event=self.event, position=op.position, force_invalidate=True, save=True
                 )