Label position in layout breaks after trying to resize the window after using QPropertyAnimation

Question

I have the following problem: I'm trying to animate a QLabel, more specifically to make it fadeIn using QPropertyAnimation. It animates successfully, but when I'm trying to resize the window, the label breaks out of the layout that's in, making it overlap with the other items. The code:

        self.label = QtWidgets.QLabel(self.frame)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label.sizePolicy().hasHeightForWidth())
        self.label.setSizePolicy(sizePolicy)
        self.label.setStyleSheet("color: #fc8102;\n"
"font-weight: bold;\n"
"font-size: 18px;")
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.setObjectName("label")

        self.opacity_effect = QtWidgets.QGraphicsOpacityEffect(self.label)
        self.opacity_effect.setOpacity(0)

        self.label.setGraphicsEffect(self.opacity_effect)

        self.anim = QtCore.QPropertyAnimation(self.opacity_effect, b'opacity')
        self.anim.setDuration(800)
        self.anim.setStartValue(0)
        self.anim.setEndValue(1)
        self.anim.start()

        self.label.setAlignment(QtCore.Qt.AlignCenter)

        self.verticalLayout.addWidget(self.label)

Image with what's happening:

Image with how it's supposed to look:

Thanks in advance.