Javascript running in edit mode only (Sharepoint 2016)

Question

On my Sharepoint 2016 page I have a list and a search function created via Script Editor that filters the list. I have this exact same code working on a Sharepoint 2013 page fine, but on this 2016 page the script doesn't work unless I go into edit mode. Sometimes after saving and leaving edit mode it will then work until I refresh the page, then it doesn't work again. I think it's because the script is running before the list has loaded. I've tried various one-line solutions including Javascript and ServicePoint functions to delay the page loading/script running which haven't worked, maybe I'm just not using them correctly. Inexperienced Coder. I've included the full Script Editor code (exluding the local jquery source):

    <div style="padding: 5px; border: 1px solid #FF5646; width: 60%; margin: 10px auto 0pt; background: none repeat scroll 0% 0% #f2f2f2; display: block;">
  <h3 style="text-align: center;">Patient Search: <input type="text&quot;" style="padding: 10px;" id="filterInput" class="filter"</h3>
</div>
</style>

<script type="text/javascript" src="http://mydomain.com/js/jquery-3.3.1.min.js">

$(document).ready(function() {

 var list = $("table.ms-listviewtable");
 // Loads the list from table
 var listItems = $("table.ms-listviewtable tr:not(.ms-viewheadertr)");
 // Filters the table
 var input = $("input#filterInput");

 input.keyup(function() // When typing the search box, the function runs...
 {
    //Insert line or function here to convert first letter to uppercase?

        listItems.each(function() // For every item in the catalogue
     {
 var text = $(this).text().toLowerCase(); // Load all the text values

 if (text.indexOf(input.val().toLowerCase()) != -1) // Compare the user input to the text value
 {
      $(this).show();// If it matches, show it
 }
 else
 {
      $(this).hide(); // If not, hide it
 }
     });
 });

 });

 </script>​​​