Logic flaw

Seems like there is a logic flaw in your script creation. Script is trying to rebuild the Shipments table with the following code

PRINT N'Rebuilding [dbo].[Shipments]'
GO
CREATE TABLE [dbo].[tmp_rg_xx_Shipments]
(
[shipmentkey] [int] NOT NULL IDENTITY(1, 1),
[orderkey] [int] NOT NULL CONSTRAINT [DF_Shipments_orderkey] DEFAULT ((0)),
[bolkey] [int] NOT NULL CONSTRAINT [DF_Shipments_bolkey] DEFAULT ((0)),
[shipno] [char] (6) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL CONSTRAINT [DF_Shipments_shipno] DEFAULT (''),
[type] [char] (1) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL CONSTRAINT [DF_Shipments_type] DEFAULT (''),
[quantity] [int] NOT NULL CONSTRAINT [DF_Shipments_quantity] DEFAULT ((0)),
[nopkg] [int] NOT NULL CONSTRAINT [DF_Shipments_nopkg] DEFAULT ((0)),
[noreels] [int] NOT NULL CONSTRAINT [DF_Shipments_noreels0] DEFAULT ((0)),
[skids] [int] NOT NULL CONSTRAINT [DF_Shipments_skids] DEFAULT ((0)),
[freight] [smallmoney] NOT NULL CONSTRAINT [DF_Shipments_freight] DEFAULT ((0)),
[grosswt] [numeric] (10, 2) NOT NULL CONSTRAINT [DF_Shipments_grosswt] DEFAULT ((0)),
[netwt] [numeric] (10, 2) NOT NULL CONSTRAINT [DF_Shipments_netwt] DEFAULT ((0)),
[entered] [smalldatetime] NOT NULL CONSTRAINT [DF_Shipments_entered] DEFAULT (''),
[readied] [smalldatetime] NOT NULL CONSTRAINT [DF_Shipments_readied] DEFAULT (''),
[assigned] [smalldatetime] NOT NULL CONSTRAINT [DF_Shipments_assigned] DEFAULT (''),
[shipped] [smalldatetime] NOT NULL CONSTRAINT [DF_Shipments_shipped] DEFAULT (''),
[readiedby] [nvarchar] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL CONSTRAINT [DF_Shipments_readiedby] DEFAULT (''),
[notified] [smalldatetime] NOT NULL CONSTRAINT [DF_Shipments_notifed] DEFAULT ('')
)
GO

Problem is that the Shipments table still exists and hence the constraints on the Shipments still exist but the CREATE TABLE statement is using the same constraint names. SQL Server throws an error about duplicate constraint names.