Wrong Item Unit In Table ER210

Description of the Issue:
While peparing a Financial Interface for the client. Done by Dorian Büdel and Manuel Wagenbach. They encountered themselfes with the following situation.

In the new table ER210, the item units are wrong.

There are two examples on debug environment already. You just need to run the SQL to recreate the issue.

Scenario on Payment Plan 118738: Downsell (Reduction Of Items between two deposit invoices)

Recreation steps:

Invoice 75172 contains a service order item "PMF 911 Turbo" with resource code TUPR with 2,0 units.

2. Reduction of order units for order item "PMF 911 Turbo" with resource code TUPR to 1,0 units.

3. Creation of invoice 75173

Issue: The table ER210 show a unit of 2, instead of 1 - or to put it differently it should show the change in ER210_RES_QTY which is 1,0 and this change also reflects in the other columns but not in this one.

You can use the following SQL to reproduce the table above due to the reason the view of the table is not existing in the backoffice:
SELECT
ER210_PAY_PLAN_ID,
ER210_PAY_NBR,
ER210_ORD_NBR,
ER210_ORD_LINE,
ER210_RES_CODE,
ER210_RES_TYPE,
ER210_STEP_EXT_CHRG,
ER210_RES_QTY
FROM
ER210_PAYMENT_PLAN_ITEMS
WHERE
ER210_ORG_CODE = '10'
AND ER210_PAY_PLAN_ID = 118738
AND ER210_PAY_NBR IN (1,2)
AND ER210_ORD_LINE = 1

As a reference, please find the following scenario, where it works fine:

Scenario on Payment Plan 118740:
Upsell (Reduction Of Items between two deposit invoices)
Recreation steps: