Issue #3116287: validateMaxLength gives bogus errors

src/Form/JobItemForm.php

@@ -311,10 +311,10 @@ class JobItemForm extends TmgmtFormBase {
    */
   public function validateMaxLength(array $element, FormStateInterface &$form_state) {
     if (isset($element['#max_length'])
-      && ($element['#max_length'] < strlen($element['#value']))) {
+      && ($element['#max_length'] < mb_strlen($element['#value']))) {
       $form_state->setError($element,
         $this->t('The field has @size characters while the limit is @limit.', [
-          '@size' => strlen($element['#value']),
+          '@size' => mb_strlen($element['#value']),
           '@limit' => $element['#max_length'],
         ])
       );