QObject, QThread, pyqt5: Error, when i trying change plain text

Question

I have a server and a client. When the server receives the data, it sends it to the client. Then I need to change the text in the "plain text" element.

class GetCallerThread(QThread):
    def __init__(self, mainwindow, parent=None):
        super(GetCallerThread, self).__init__(parent)
        self.mainwindow = mainwindow

    def run(self):
        consumer = KafkaConsumer('client', bootstrap_servers=['localhost:29092'])
        for message in consumer:
            mess = message.value.decode()
            self.mainwindow.run_page_plainTextEdit.setPlainText(mess)
            self.mainwindow.show()


class Window(QMainWindow, Ui_Application):
    tray_icon = None

    def __init__(self, parent=None):
        super().__init__(parent)
        self.setup_ui = self.setupUi(self)
        self.center()

        self.get_caller_thread_instance = GetCallerThread(mainwindow=self)
        self.get_caller_thread_instance.start()

    # Init main window
    def login_window(self):
        dialog = MainWindow(self)
        dialog.exec()


class MainWindow(QDialog):
    def __init__(self, parent=None):
        super().__init__(parent)
        loadUi("ui/main_window.ui", self)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    win = Window()
    win.setWindowTitle("App")
    win.show()
    sys.exit(app.exec())

P.S. This is not the first such problem with stack flow, but I do not know how to fix it. Please, help me.