Hi,
of course they are empty.
The elements with relevance "0" are not posted.
Either you hide these two subquestions by javascript or - the easy way -
set the values by a hidden question of type equation after this question.
{A_EUR="7"}
{A_Leistung="This is fixed"}
By the way: What is the reason to have two hidden elements with constant values?
I revise your question text and the validation.
In my opinion it's not the best to show initially an error.
Joffm