dual arrow artefact when setting QToolButton border: none

Whenever setting the border to none the drop down arrow is duplicated according to the appended image.

Raw code:
#  coding: utf-8 

################################################################################
## Form generated from reading UI file 'ui.ui'
##
## Created by: Qt User Interface Compiler version 6.1.2
##
## WARNING! All changes made in this file will be lost when recompiling UI file!
################################################################################

import sys
from PySide6.QtCore import *  # type: ignore
from PySide6.QtGui import *  # type: ignore
from PySide6.QtWidgets import *  # type: ignore

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        if not MainWindow.objectName():
            MainWindow.setObjectName(u"MainWindow")
        MainWindow.resize(287, 107)
        self.centralwidget = QWidget(MainWindow)
        self.centralwidget.setObjectName(u"centralwidget")
        self.verticalLayout = QVBoxLayout(self.centralwidget)
        self.verticalLayout.setObjectName(u"verticalLayout")
        self.toolButton = QToolButton(self.centralwidget)
        self.toolButton.setObjectName(u"toolButton")
        self.toolButton.setStyleSheet(u"border: none")
        self.toolButton.setCheckable(True)
        self.toolButton.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
        self.toolButton.setArrowType(Qt.DownArrow)

        self.verticalLayout.addWidget(self.toolButton)

        self.verticalSpacer = QSpacerItem(20, 40, QSizePolicy.Minimum, QSizePolicy.Expanding)

        self.verticalLayout.addItem(self.verticalSpacer)

        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QMenuBar(MainWindow)
        self.menubar.setObjectName(u"menubar")
        self.menubar.setGeometry(QRect(0, 0, 287, 21))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QStatusBar(MainWindow)
        self.statusbar.setObjectName(u"statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)

        QMetaObject.connectSlotsByName(MainWindow)
    # setupUi

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QCoreApplication.translate("MainWindow", u"MainWindow", None))
        self.toolButton.setText(QCoreApplication.translate("MainWindow", u"hello", None))
    # retranslateUi

class MainWindow(QMainWindow):
    def _init_(self):
        super(MainWindow, self)._init_()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

if _name == "main_":
    app = QApplication(sys.argv)

    window = MainWindow()
    window.show()

    sys.exit(app.exec())