Unusual SQL Server Query Result - sql-server-2008

Question

I faced with an unusual query result while running a sql server query.
The important table to note is Code_Structure_Type.
It contains columns Code_Structure_Type_Id smallint, Name char(50) and few other columns that are not used here.
My Query
SELECT DISTINCT A1.A1_Id AS Code_Unit_Attribute_Id,
A1.Name AS Code_Unit_Attribute_Name,
Code_Structure_Type.A1_Name AS Code_Attribute_Type
--, Code_Structure_Type.Code_Structure_Type_Id
FROM Defect
INNER JOIN Defect_Code_Unit
ON Defect.Defect_Id = Defect_Code_Unit.Defect_Id
INNER JOIN Code_Unit
ON Defect_Code_Unit.Code_Unit_Id = Code_Unit.Code_Unit_Id
INNER JOIN A1
ON Code_Unit.A1_Id = A1.A1_Id
INNER JOIN ERA_Module
ON Defect.ERA_Module_Id = ERA_Module.ERA_Module_Id
INNER JOIN Code_Unit_Type
ON Code_Unit.Code_Unit_Type_Id = Code_Unit_Type.Code_Unit_Type_Id
INNER JOIN Code_Structure_Type
ON Code_Unit_Type.Code_Structure_Type_Id = Code_Structure_Type.Code_Structure_Type_Id
WHERE ERA_Module.ERA_Project_Id = 472
AND ERA_Module.Is_Active = 1
AND Defect.Is_Closed = 0
AND Defect_Code_Unit.Is_Active = 1
AND Code_Structure_Type.Name = 'Pega Rules'
--AND Code_Structure_Type.Code_Structure_Type_Id = 2
AND A1.A1_Id > 0
AND Code_Unit.Scope_Id = 1
This query returns me with a single row which is incorrent. The expected result of this query should be none because we do not have Defects for 'Pega Rules' Code_Structure_Type.
If I uncomment this line
--, Code_Structure_Type.Code_Structure_Type_Id
I get no results which is correct.
Also if I filter from the Code_Structure_Type_Id which is for 'Pega Rules' not with Code_Structure_Type.Name I get the correct result as well which is none.
To do this I uncomment this line
--AND Code_Structure_Type.Code_Structure_Type_Id = 2
and comment this line
AND Code_Structure_Type.Name = 'Pega Rules'
So basically I'm doing the same thing and there is no other name like 'Pega Rules' in the table Code_Structure_Type, not even close. Only five rows are there in that table.
I need to understand what is happening here.
Thanks in advance.
Links to Execution Plans
Files, when used 'pega rules' only - incorrect_original.xml when used 'pega rules' + select - correct_with_added_select.xml when used id - correct_with_Id.xml