GroupTermOperationProvider should call the parents

GroupTermOperationProvider is part of the operation provider decorator chain. By not calling the parent, you are eliminating part of that chain.

Consider changing:

  /**
   * {@inheritdoc}
   */
  public function getGroupOperations(GroupInterface $group) {

    $vocabulary_id = $this->groupRelationType->getEntityBundle();
    $vocabulary = Vocabulary::load($vocabulary_id);
    $operations = [];

to

  /**
   * {@inheritdoc}
   */
  public function getGroupOperations(GroupInterface $group) {

    $vocabulary_id = $this->groupRelationType->getEntityBundle();
    $vocabulary = Vocabulary::load($vocabulary_id);
    $operations = $this->parent->getGroupOperations($group);