Thank u, that was the Answer I want to hear 🙂 . Your hint with the delayValidation Property works fine. But your 2nd sentence was the answer of my question
As far as I know the validation errors you are seeing are considered non-fatal so SQL Agent carries on as usual.
This is right, the problem why I didn't find the expected results was, that someone changed the Package Configuration to another path. So the Package works - despite of the error.
Thank you