Field mapping does not work as expected in node-red-contrib-oracledb-mod

i'm using the contrib node for Oracle DB to insert some values into the database.
There was already a thread with a similar issue: (Writing Insert query inside node-red-contrib-oracledb-mod).
The incoming msg.payload of the Oracle node is a nested object

Time: "2023-02-05T19:51:17"
ED300L: object
Total_in: 9627.902
Power_cur: 681
Total_out: 27910.92
Meter_id: "02560000000000"

I can copy the path to each of these elements into the field mapping of the node


In the query I reference the four elements using bind variables

insert into stromzaehler (zeitpunkt, bezug, aktuell, lieferung)
values (:zeitpunkt, :bezug, :aktuell, :lieferung)

Executing the flow only null values will be inserted into the database table.
Any ideas what could have been going wrong here?