Javascript in file running intermittently

Question

I am using javascript to perform ajax requests every time an item is selected in a combo. For this the Select tag executes the Onchange event.

However, I am having problems calling the js function that is working intermittently. Sometimes the value is changed and the function is not executed.

This is the JS snippet that should be run every time select is changed:

$(document).ready(function () {

    $('.tbl select.detalhes').change(function () {
        if ($(this).val() != "") {
            var id = $(this).val();
            AjaxCall(urlPrefix + 'Detalhe.aspx/Ficha', '{ id: ' + id + ' }', function (data) {
                carregarFicha(data);
            });
            $(this).prop('selectedIndex', 0);
        }
    });

cshtml code where I insert the html in @Section Head:

@model IList<Round>
@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/SiteLayout.cshtml";
}
@section Head
{
	<script src="@Url.NonCached("~/Scripts/Index.js")" type="text/javascript"></script>
}

@if (Model != null && Model.Count > 0)
{
    <h2>Rodada</h2>    
    var textoRodadas = @Model.Count > 0 ? "Rodadas encontradas" : "Rodada encontrada";         
    <span class="total-registros"> <strong>@Model.Count</strong> @textoRodadas</span>    
    <table border="0" cellpadding="0" cellspacing="0" class="tbl" id="table-round">
		<thead>
			<tr>
				<th scope="col" class="ord">Rodada</th>
				<th scope="col" class="ord">Data Inicial</th>
				<th scope="col" class="ord">Data Final</th>
				<th scope="col" width="150" class="ord tits-th col-escura ">Regras</th>				
			</tr>
		</thead>
		<tbody>
		
        @for (int i = 0; i < Model.Count; i++)
        {
		
			var item = Model[i];
            var classe = "class=\"" + item.Tipo.ToString();
            if (item.Protegido == SimNao.Sim)
            {
                classe += " protegido ";
            }
            classe += i % 2 == 0 ? "\"" : " odd\"";

            var permitirCriarRegraComLances = !(item.Tipo == App.AdjudicacaoInicial);
                
            <tr @Html.Raw(classe) >
				<td class="tbl-nomeTipo-round") ">
					@Html.Hidden("id", item.Id)
					<span class="click-round tbl-nome-round">@item.Nome</span>
				</td>
				<td class="click-round tbl-data-round">
					@item.DataInicio.ToString("dd/MM/yyyy")
				</td>
				<td class="click-round tbl-data-round">
					@item.DataFim.ToString("dd/MM/yyyy")
				</td>
				<td class="col-escura">
				  <div  class="grid-12-12 form">
				  @{
						var regras = item.Regras.OrderBy(t => t.Nome).ToArray();
				  }
				  <span class="txt-maior ">@regras.Length</span>
				  @if (regras.Length > 0)
				  {
					<select class="form-txt regras" id="reg1" onchange="mudou(this)">
						<option value="" >Selecione</option>
					  @foreach (var reg in regras)
					  {
							<option value="@reg.Id">@reg.Nome</option>   
					  }
					</select>
				  }
					
				  </div>					
				</td>
			</tr>            
        }
		</tbody>
	</table>
}
else
{
	<span>Sem resultados</span>
}

UPDATE

No longer working properly or embedding JS directly into cshtml instead of referencing the file.

UPDATE 2

I forgot to mention that the application is only approved for Firefox and that the code worked correctly until the company updated some customers with version 60.7.0. This particular version is what should be causing the problem. I already suggested the upgrade, but the company has many bureaucracies and the below controls the upgrades.