Enter Key in text field causing Nintex Classic form to close without saving

This is the code I use to prevent that while also allowing us to use the Enter key to insert new lines while inside of a Multiline Text Control:

NWF$(window).on("keydown", function (event) {
  var target = (event.target || event.srcElement);
  if (event.keyCode === 13) {
    event.preventDefault();
    if (target.nodeName.toLowerCase() === "textarea") {
      var textValue = target.value;
      var textBeforeSplit = textValue.slice(0, target.selectionStart);
      var textAfterSplit = textValue.slice(target.selectionEnd, textValue.length);
      var resultingText = textBeforeSplit + "\n" + textAfterSplit;
      target.value = resultingText;
      target.selectionStart = target.textLength - textAfterSplit.length;
      target.selectionEnd = target.selectionStart;
    }
  }
});

Just throw that into the custom JS on a classic form and let me know if it works for ya