Unsolved Program doesn't completely quit

returns

worker->stop(); //sets boolean cancel to true to let worker finish its work

workerThread->quit();

void ReplicatorMainScreen::closeEvent(QCloseEvent *event)
{
    emit stopWork();
    event->accept();
}

void ReplicatorMainScreen::setupBackend(Replicator *rep)
{
    connect(ui->backupSelectedButton,SIGNAL(clicked(bool)),rep,SLOT(selectedBackup()));
    connect(this,SIGNAL(stopWork()),rep,SLOT(stopWork()));
    connect(ui->cancelButton,SIGNAL(clicked(bool)),rep,SLOT(cancelBackup()));
}

void Replicator::cancelBackup()
{
    if (isBusy)
        worker->stop();
}

void Replicator::stopWork()
{
    quitting = true;
    if (isBusy)
        worker->stop(); //sets boolean cancel to true to let worker finish its work
}

void Worker::stop() { cancel = true; } // cancel is std::atomic_bool

void Replicator::selectedBackup()
{
    isBusy = true;
    emit backup(jobList,simpleJobs);
}

void Worker::backup(QList<BackupJob> passJobs, QList<BackupJob> passSimpleJobs)
{
    jobs = passJobs;
    simpleJobs = passSimpleJobs;
    startJobScans(); //these check for cancel condition and abort if true
    startJobBackups(); // this too
    emit backupFinished(JobType::Normal, cancel, errorsFound);
}

void Replicator::backupDone()
{
    isBusy = false;
}

Replicator::~Replicator()
{
    workerThread->quit();
    workerThread->wait();
}

Replicator::Replicator(QWidget *parent) :
    QWidget(parent)
{
    workerThread = new QThread(this);
    workerThread->start();
    worker = new Worker;
    worker->moveToThread(workerThread);
    mainScreen = new ReplicatorMainScreen;
    setupWorker();
    mainScreen->setupBackend(this);
}

void Replicator::setupWorker()
{
    connect(this, SIGNAL(backup(QList<BackupJob>,QList<BackupJob>)), worker, SLOT(backup(QList<BackupJob>,QList<BackupJob>)));
    connect(worker, SIGNAL(backupFinished(JobType,bool,bool)), this, SLOT(backupDone(JobType,bool,bool)));
    connect(workerThread, SIGNAL(finished()), worker, SLOT(deleteLater()));
}