Fix broken deletion

freqtrade/persistence/custom_data.py

@@ -96,6 +96,10 @@ class CustomDataWrapper:
         if not CustomDataWrapper.use_db:
             CustomDataWrapper.custom_data = []
 
+    @staticmethod
+    def delete_custom_data(trade_id: int) -> None:
+        _CustomData.session.query(_CustomData).filter(_CustomData.ft_trade_id == trade_id).delete()
+
     @staticmethod
     def get_custom_data(key: Optional[str] = None,
                         trade_id: Optional[int] = None) -> List[_CustomData]:

freqtrade/persistence/trade_model.py

@@ -1600,8 +1600,7 @@ class Trade(ModelBase, LocalTrade):
         for order in self.orders:
             Order.session.delete(order)
 
-        for entry in self.custom_data:
+        CustomDataWrapper.delete_custom_data(trade_id=self.id)
-            _CustomData.session.delete(entry)
 
         _CustomData.session.commit()
         Trade.session.delete(self)