Combining Three Selects into One - sql

Question

I've been trying to consolidate these three SQL functions into one.
Functions
Function 1
`ALTER FUNCTION [dbo].[Fn_Get_User] (#_CompanyKey INT)
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE #UserIDs AS VARCHAR(8000);
SET #UserIDs = '';
SELECT #UserIDs = #UserIDs + ', ' + x.User_ID
FROM
(SELECT DISTINCT UPPER(p.User_ID) as User_ID
FROM [dbo].[Program] AS p WITH (NOLOCK)
WHERE p.CompanyKey = #_CompanyKey
UNION
SELECT DISTINCT UPPER(ps.User_ID) as User_ID
FROM [dbo].[Program] AS p WITH (NOLOCK)
LEFT OUTER JOIN [dbo].[Program_Scenario] AS ps WITH (NOLOCK)
ON p.ProgramKey = ps.ProgramKey
WHERE p.CompanyKey = #_CompanyKey
AND ps.User_ID IS NOT NULL) x
RETURN Substring(#UserIDs, 3, 8000);
END`
Function 2
`ALTER FUNCTION [dbo].[Fn_Get_Source] (#_CompanyKey INT)
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE #System_IDs AS VARCHAR(8000);
SET #System_IDs = '';
SELECT #System_IDs = #System_IDs + ', ' + Original_Source_System_ID
FROM (
SELECT DISTINCT p.Original_Source_System_ID
FROM [dbo].[Program] AS p WITH (NOLOCK)
WHERE p.CompanyKey = #_CompanyKey
) a
RETURN Substring(#System_IDs, 3, 8000);
END`
Function 3
`ALTER FUNCTION [dbo].[Fn_Get_ContractNbr] (#_CompanyKey INT)
RETURNS VARCHAR(8000)
AS
BEGIN
DECLARE #ContractNums AS VARCHAR(8000);
SET #ContractNums = '';
SELECT #ContractNums = #ContractNums + ', ' + bi.Contract_Nbr + '-' +
ISNULL(CAST(bi.Year_Nbr AS varchar(8)),'') + '-' +
ISNULL(CAST(bi.Layer_Nbr AS varchar(8)),'')
FROM [dbo].[Program] AS p WITH (NOLOCK)
INNER JOIN [dbo].[Program_Scenario] AS ps WITH (NOLOCK) ON p.ProgramKey = ps.ProgramKey
INNER JOIN [dbo].[Layer] AS l WITH (NOLOCK) ON ps.ProgramScenarioKey = l.ProgramScenarioKey
INNER JOIN [dbo].[Bound_Information] AS bi WITH (NOLOCK) ON l.LayerKey = bi.LayerKey
AND ISNULL(bi.Contract_Nbr,'') <> '' --IS NOT NULL
WHERE p.CompanyKey = #_CompanyKey
RETURN Substring(#ContractNums, 3, 8000);
END`
My attempted Solution
`SET STATISTICS TIME ON
SELECT DISTINCT UPPER((p.User_ID) +', '+ ps.User_ID) as UserID,
bi.Contract_Nbr as ContractNumber,
p.Original_Source_System_ID as SourceSysID,
ISNULL(CAST(bi.Year_Nbr AS varchar(8)),'') as UW_Year,
ISNULL(CAST(bi.Layer_Nbr AS varchar(8)),'') as LayerNumber,
p.CompanyKey,
ps.ProgramKey,
c.Company_Name
FROM
[dbo].[Program] AS p WITH (NOLOCK)
INNER JOIN [dbo].[Program_Scenario] AS ps WITH (NOLOCK)
ON p.ProgramKey = ps.ProgramKey
INNER JOIN [dbo].[Layer] AS l WITH (NOLOCK) ON ps.ProgramScenarioKey = l.ProgramScenarioKey
INNER JOIN [dbo].[Bound_Information] AS bi WITH (NOLOCK) ON l.LayerKey = bi.LayerKey
INNER JOIN [dbo].[Company] AS c with (NOLOCK) ON p.CompanyKey = c.CompanyKey
AND ISNULL(bi.Contract_Nbr,'') <>''
AND ps.User_ID IS NOT NULL
WHERE p.CompanyKey between 2 and 100000
ORDER BY ProgramKey`
My data-set is 20k+ rows so I'm unable to share it here, but where I'm struggling is my function is not returning the same amount of rows as the above three functions. Might there be anything anyone sees to possibly solve this issue? (24755 rows vs. 24052 rows respectively)