Delete add-ons explicitly

src/pretix/base/services/orders.py

@@ -1024,6 +1024,7 @@ class OrderChangeManager:
                         'addon_to': opa.addon_to_id,
                         'old_price': opa.price,
                     })
+                    opa.delete()
                 self.order.log_action('pretix.event.order.changed.cancel', user=self.user, auth=self.auth, data={
                     'position': op.position.pk,
                     'positionid': op.position.positionid,

src/tests/presale/test_cart.py

@@ -1679,6 +1679,20 @@ class CartAddonTest(CartTestMixin, TestCase):
             }
         ])
 
+    def test_remove_with_addons(self):
+        cp1 = CartPosition.objects.create(
+            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            event=self.event, cart_id=self.session_key
+        )
+        cp2 = CartPosition.objects.create(
+            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            event=self.event, cart_id=self.session_key, addon_to=cp1
+        )
+        self.cm.remove_item(cp1.pk)
+        self.cm.commit()
+        assert not CartPosition.objects.filter(pk=cp1.pk).exists()
+        assert not CartPosition.objects.filter(pk=cp2.pk).exists()
+
     def test_remove_addons(self):
         cp1 = CartPosition.objects.create(
             expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),