Hi Weber,
The reason why you are seeing this behavior is because the file path 'pfad' that you are passing to the 'Read from XML.vi' is sending the old value (it's current value right when you value change happens). To ensure that the new value is sent, please see my attached VI. I am using the newValue input node from the event structure to send it to the 'Read from XML.vi'.
I hope this helps.
Feroz