Hello, exactly the same thing happens to me.
I’m trying to understand what is said in this post since the problem is the same, in case it helps you: https://community.openai.com/t/assistant-can-not-search-the-whole-file-using-file-search/739661
According to the post and my understanding, it seems that this behavior of the assistant is normal and that the solution for structured data types is implement function-calling.