Trying to aggregate quantities across multiple tables SQL - sql

Question

I'm building a stock synch which compares product quantities from three different tables:
EWM
USOR
DSOR
The maths behind the stock synch is EWM - (USOR + DSOR) = Misalignment
The EWM table divides the product quantities by the different storage types that products are held in which necessitates the need to have the quantities aggregated before being used in the end query but I keep getting the wrong figure after aggregating the quantities so I think I'm doing something wrong but I can't seem to spot it.
Here's my code:
--Table for EWM Data--
create table EWM(
Date_loaded date,
Sap_code bigint,
Product_description varchar(100),
Location nvarchar(50),
Storage_type varchar(50),
Quantity int,
Sap_batch nvarchar(50),
Expiry_date date,
Stock_type varchar(50)
);
--Table for USOR Data--
create table USOR(
Date_Loaded date,
Sap_Code bigint,
Product_description varchar(100),
Pack nvarchar(50),
Cost_price decimal,
Trade_price decimal,
Stock int,
Location nvarchar(50),
);
--Table for DSOR--
create table DSOR(
Date_Loaded datetime,
Sap_code bigint,
Product_description varchar(100),
Bin_location nvarchar(50),
Location varchar(50),
Pack nvarchar(50),
Units int,
Total int,
);
--Table for difference between EWM and USOR+DSOR--
create table Misalignment
(
Date_loaded date,
Sap_code bigint,
Product_description varchar(100),
Pack nvarchar(50),
Location nvarchar(50),
Total_difference int
)
--Inserting data in Misalingment using query from USOR, USOR_DSOR, EWM --
WITH x AS (
SELECT SAP_Code, Quantity
FROM EWM
GROUP BY SAP_Code, Quantity
)
insert into Misalignment(Date_Loaded, Sap_code, Product_description, Location, Total_difference)
Select USOR.Date_Loaded, USOR.Sap_Code, USOR.Product_description, USOR.Location, sum(x.Quantity - (USOR.stock + DSOR.Total))as Total_difference
FROM x
INNER JOIN USOR ON x.SAP_Code = USOR.SAP_Code
INNER JOIN DSOR ON x.SAP_Code = DSOR.SAP_Code
group by USOR.Date_Loaded, USOR.Sap_Code, USOR.Product_description, USOR.Pack, USOR.Location
select * from Misalignment
where Total_difference > 0
order by Total_difference
desc
I ran the query below to test my code out:
select * from ewm
where Date_loaded = '2020-10-05' and Sap_code = 1002945
select * from DSOR
where Sap_code = 1002945 and Date_loaded= '2020-10-05'
select * from Misalignment
where Sap_code = 1002945 and Date_loaded = '2020-10-05'
This was the result:
The actual result should be 0.
Any suggestions?