[Python] How to get rid of the extra corner on the right bottom of QComboBox with PyQt?

I am working on a combobox with PyQt. I am expecting to have round corners on the dropdown. Here is what it looks like now:



As it shows, there is a white corner with 0 radius on the bottom right. What is confusing is that when I place the window on top of a black background, the extra would "go away" or maybe it is just black:



I tried it with other colors and it is hard to tell what color that corner would turn into:



Does anyone know what might be the cause of that extra corner, or how to remove it?

Here is my code:

self.label = QLabel("smething")

self.combobox = QComboBox()
self.combobox.addItems(["1","2","3","4"])

vbox = QVBoxLayout(self)
vbox.addWidget(self.label)
vbox.addWidget(self.combobox)

widget = QWidget(self)
widget.setLayout(vbox)

self.resize(200,100)
widget.resize(200,100)

self.combobox.view().window().setWindowFlags(Qt.Popup | Qt.FramelessWindowHint)
self.combobox.view().window().setAttribute(Qt.WA_TranslucentBackground)

self.setStyleSheet("""
QComboBox {
background-color: black;
color: #00ff00;
selection-background-color: transparent;
border: 1.5px solid #00ff00; /* Border color and thickness */
border-radius: 5px; /* Rounded corners of the button */
padding: 5px;
}
QComboBox editable {
background-color : yellow;
}
QComboBox QAbstractItemView {
color: #00ff00; /* Text color of the drop-down items */
background-color: red; /* Optional: Set background color of the drop-down list */
border: 1.5px solid #00ff00; /* Border of the drop-down list */
border-radius: 10px; /* Rounded corners for the drop-down list */
selection-background-color: #00ff00;
selection-color: red;
padding: 5px;
}
""")

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