diff --git a/modules/purchase_trade/sale.py b/modules/purchase_trade/sale.py
index cf829d3..a82eb55 100755
--- a/modules/purchase_trade/sale.py
+++ b/modules/purchase_trade/sale.py
@@ -1090,7 +1090,23 @@ class SaleLine(metaclass=PoolMeta):
         for line in lines:
             from_del = values.get('from_del', getattr(line, 'from_del', None))
             to_del = values.get('to_del', getattr(line, 'to_del', None))
+            logger.info(
+                "SALE_LINE_DELIVERY_PERIOD_CHECK line=%s values=%s "
+                "current_from=%s current_to=%s computed_from=%s computed_to=%s",
+                getattr(line, 'id', None),
+                values,
+                getattr(line, 'from_del', None),
+                getattr(line, 'to_del', None),
+                from_del,
+                to_del,
+            )
             if from_del and to_del and from_del > to_del:
+                logger.info(
+                    "SALE_LINE_DELIVERY_PERIOD_INVALID line=%s from=%s to=%s",
+                    getattr(line, 'id', None),
+                    from_del,
+                    to_del,
+                )
                 raise UserError(
                     "Delivery period From date must be before To date.")
 
@@ -1604,9 +1620,15 @@ class SaleLine(metaclass=PoolMeta):
 
     @classmethod
     def write(cls, *args):
+        logger.info("SALE_LINE_WRITE_START args=%s", args)
         actions = iter(args)
         args = []
         for records, values in zip(actions, actions):
+            logger.info(
+                "SALE_LINE_WRITE_GROUP records=%s values=%s",
+                [getattr(record, 'id', None) for record in records],
+                values,
+            )
             cls._check_delivery_period_values(records, values)
             args.extend((records, values))