Why sometimes the name="btnI" doesn't work like proper google's "I'm Feelin Lucky" button?

Question

The problem is with this type of code:

<form class="google_search_form_1" action="https://google.com/search">
    <div class="google_search_div_3_1">
        <div class="google_search_div_3_1_1">
            <input class="google_search_text_input_1" maxlength="2048" name="q" type="text" title="Search">
        </div>
        <div class="google_search_div_3_1_2">
            <input class="google_search_submit_button_1" value="Google Search" name="btnK" type="submit">
            <input class="google_search_im_feeling_lucky_button_1" value="I'm Feeling Lucky" name="btnI" type="submit">
        </div>
    </div>
</form>

The issue is exactly with "I'm Feeling Lucky" button. Some words that have, as i've noticed, results that begin with google map snippet or google translate snippet don't redirect to the first page. But when that search input provides first link as a normal page then it works just fine.

Can somebody explain why that is happening, or what code excerpt should be responsible for it, or how to handle it?

I will be very grateful for all your help!