SQL Server 2017 - Update NVARCHAR(MAX) column causes question marks

Question

EDIT:
I tried to simplify my question without success by not adding the entire script, after getting unrelated answers to my question I added the entire script.

DDL for CountryTabs Table:

CREATE TABLE [dbo].[CountryTabs](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [CountryID] [int] NULL,
    [LanguageType] [smallint] NOT NULL,
    [Name] [nvarchar](200) NOT NULL,
    [Content] [nvarchar](max) NULL,
    [CategoryOrder] [smallint] NOT NULL,
    [Status] [int] NOT NULL,
PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO

--find out how many occurnces
DECLARE @OccurnceTbl table(ID int, Content nvarchar(max),Occurnce int)
INSERT into @OccurnceTbl
SELECT ID,Content, LEN(Content) - LEN(REPLACE(Content, 'http://www.example.com/country_page.asp?countryID=','http://www.example.com/country_page.asp?countryID')) AS count    
FROM CountryTabs where ID = 71


DECLARE @Occurnce int;
SELECT @Occurnce = Occurnce From @OccurnceTbl
DECLARE @Counter int = 0;
 WHILE (@Counter < @Occurnce)
    Begin
        DECLARE @ID int;
        DECLARE @Content nvarchar(max);
        DECLARE @NewContent nvarchar(max);
        SELECT @ID = ID from @OccurnceTbl
        SELECT @Content = Content from CountryTabs where ID = @ID

DECLARE @startIndex int = PATINDEX(N'%http://www.example.com/country_page.asp?countryID%',@Content);

DECLARE @contentWithoutStart NVARCHAR(max) = SUBSTRING(@Content, @startIndex, LEN(@Content))

DECLARE @endIndex int = PATINDEX(N'%">%', @contentWithoutStart) + @startIndex-1;

DECLARE @lengthToReplace int =  @endIndex - @startIndex;

DECLARE @strToReplace nvarchar(500) = SUBSTRING(@Content , @startIndex , @lengthToReplace);
SELECT @NewContent = REPLACE(@Content, @strToReplace ,'https://example-new.com')

UPDATE CountryTabs set Content = @NewContent where ID = @ID

SET @Counter = @Counter + 1;

--Select @startIndex,@endIndex,@lengthToReplace,@Counter,@strToReplace

End

Result is many question marks???????? except for the places where

https://example-new.com

Content Column:

Content nvarchar    no  -1  yes (n/a)   (n/a)   SQL_Latin1_General_CP1_CI_AS

The Content column in the table CountryTabs is of type NVARCHAR(MAX) and it already contains chars properly stored without question marks, only after the update they appear.

What am I missing here?

Answer 1

I'm keen to know if this works as expected:

DECLARE @Content nvarchar(max);
SELECT @Content = Content from CountryTabs where ID = @ID
DECLARE @NewContent nvarchar(max);
DECLARE @strToReplace nvarchar(500) = N'http://www.example.com';
SELECT @NewContent = REPLACE(@Content, @strToReplace ,N'https://new-example.com')

UPDATE CountryTabs set Content = @NewContent where ID = @ID


SELECT Content from CountryTabs where id = @ID