SELECT2 is not returning pre-selected item value

Question

When changing a Select2 option, it is returning all the data correctly, but when I go back to the previous option (which was already selected), it is not searching the values correctly.

Exemplifying better:

I have a "change" form with a Select2 that comes pre-selected with the current value (value01) pulled from the database. So far so good, but when I give a "change" in Lect2 (valu02), it has to change the "price" field in the same form. This part, quiet, I’m doing perfectly. But when I change Select2 again to (value01) it should return the previous price, but this value returns "Undefined", as if it had used a "cache", even though I have the cache as false.

Code of my Lect2:

(function($){
    $.fn.selects = function(urlcontent, tamanho='1', holder=''){
        $(this).select2( {
            width: '100%',
            selectionTitleAttribute: false,
            minimumInputLength: tamanho,
            language: "pt-BR",
            cache: false,
            escapeMarkup: function (markup) {
                return markup;
            },
            placeholder: holder,
            selectOnClose: true,
            ajax: {
                url: urlcontent,
                type: "post",
                dataType: 'json',
                delay: 250,
                data: function (params) {
                   return {
                      searchTerm: params.term // search term
                   };
                },
                processResults: function (response) {
                   return {
                      results: response
                   };
                }
            }
        });
    };
})(jQuery);

Call from the Select2:

$('#id_produto').selects("classes/self_preco.php",0,"Selecione...");
$('#id_produto').change(function(e) {
    $('#preco').val($(this).select2('data')[0]['preco']);
});

self_preco.php

while($reply = mysqli_fetch_object($con)){
    $response[] = array(
        "id" => $reply->iddado,
        "text" => $reply->produtodetalhe,
        "preco" => floatForce($reply->preco)
    );
}

echo json_encode($response);
exit();