wp_dropdown_categories() scripts working erratically on sidebar

The reason that the original code is not working is because each category dropdown <select> element has an HTML id of cat. The JavaScript snipets are looking for the element with the ID of cat, but there are 3 of them. IDs should always be unique in the markup.

wp_dropdown_categories() does allow the id to be customized, so we can add a unique id to each category dropdown and make the appropriate adjustments to the JS:

<div class="sidebarItem">
     <h4>Model Type</h4>
     <?php wp_dropdown_categories('show_option_none=Select model type&include=18,19,20,21&id=model_type'); ?>

     <script type="text/javascript"><!--
        var dropdownModel = document.getElementById("model_type");
        function onCatChangeModel() {
           if ( dropdownModel.options[dropdownModel.selectedIndex].value > 0 ) {
              location.href = "https://wordpress.stackexchange.com/questions/253697/<?php echo get_option("home');
     ?>/?cat="+dropdownModel.options[dropdownModel.selectedIndex].value;
           }
        }
        dropdownModel.onchange = onCatChangeModel;
     --></script>
  </div>

  <div class="sidebarItem">
     <h4>Year Produced</h4>
     <?php wp_dropdown_categories('show_option_none=Select year produced&include=7,8,9,10,11,12,13,14,15,16,17&id=year_produced'); ?>

     <script type="text/javascript"><!--
        var dropdownYear = document.getElementById("year_produced");
        function onCatChangeYear() {
           if ( dropdownYear.options[dropdownYear.selectedIndex].value > 0 ) {
              location.href = "https://wordpress.stackexchange.com/questions/253697/<?php echo get_option("home');
     ?>/?cat="+dropdownYear.options[dropdownYear.selectedIndex].value;
           }
        }
        dropdownYear.onchange = onCatChangeYear;
     --></script>
  </div>

  <div class="sidebarItem">
     <h4>Identified/Unidentified</h4>
     <?php wp_dropdown_categories('show_option_none=Select status&include=22,23&id=identified_status'); ?>

     <script type="text/javascript"><!--
        var dropdownStatus = document.getElementById("identified_status");
        function onCatChangeStatus() {
           if ( dropdownStatus.options[dropdownStatus.selectedIndex].value > 0 ) {
              location.href = "https://wordpress.stackexchange.com/questions/253697/<?php echo get_option("home');
     ?>/?cat="+dropdownStatus.options[dropdownStatus.selectedIndex].value;
           }
        }
        dropdownStatus.onchange = onCatChangeStatus;
     --></script>
  </div>