Cannot handle QKeyEvent normally in QPlainText KeyPressEvent

I inherited QPlainTextEdit and reimplement KeyPressEvent(QKeyEvent) to print info.

void PlainTextEdit::keyPressEvent(QKeyEvent *e)
{
    qDebug()<< "-------------PlainTextEdit--------------";
    qDebug()<< "QKeyEvent Text:"<<e->text();
    qDebug()<< "QKeyEvent Count:"<<e->count();
    qDebug()<< "QKeyEvent isAutoRepeat:"<<e->isAutoRepeat();
    if(e->modifiers().testFlag(Qt::ShiftModifier)){qDebug()<<"QKeyEvent modifier:"<<"ShiftModifier";}
    qDebug()<< "QKeyEvent key:"<<e->key();
    return QPlainTextEdit::keyPressEvent(e);
}

bug trigger step:

1.press shift and don't release,the key keyPressEvent will be called.

2.press $ (which is 4 without shift, same as other numbers key) ,then haven't call keyPressEvent ,the PlainTextEdit shows a  $.

Press shift  twice in a row ,then press shift and number key (not at the Numeric keypad), the key keyPressEvent will be called normally.Then press shift twice in a row,it will back to the wrong status.