QSlider handle does not move programmatically after moving the handle manually

Question

I have a slider that can be controlled by rewind/forward buttons or manually. When I start the application, clicking the buttons works fine and the slider moves as desired. However, if I drag the slider handle to a given position, the buttons still trigger the valueChanged event but the position of the handle is not updated on the screen. I noticed that if I double click the handle, the handle starts to move again according to the buttons.

I could overcome this problem by simulating a mouse click (with QMouseEvent), but it seems a bit of a hack and maybe there's a better solution I could not figure out.

Here's my code:

from PyQt5.QtWidgets import QSlider, QHBoxLayout, QLabel, QWidget, QToolButton
from PyQt5.Qt import Qt, QStyle


class TimeSliderWidget(QWidget):

    def __init__(self):
        super().__init__()

        self._createWidgets()
        self._configureLayout()

    def setTimeSteps(self, timeSteps: int):
        self._timeSlider.setRange(0, timeSteps - 1)

    def reset(self):
        self._timeSlider.setValue(0)

    def setEnabled(self, enabled: bool):
        self._timeSlider.setEnabled(enabled)
        if enabled:
            self._updateButtonsState(self._timeSlider.value())
        else:
            self._rewindButton.setEnabled(False)
            self._forwardButton.setEnabled(False)

    def value(self):
        return self._timeSlider.value()

    def _createWidgets(self):
        self._timerLabel = QLabel("0")
        self._timeSlider = QSlider(Qt.Horizontal)
        self._timeSlider.setSingleStep(1)
        self._timeSlider.valueChanged.connect(self._onValueChange)
        self._rewindButton = QToolButton()
        self._rewindButton.setIcon(self.style().standardIcon(QStyle.SP_MediaSeekBackward))
        self._forwardButton = QToolButton()
        self._forwardButton.setIcon(self.style().standardIcon(QStyle.SP_MediaSeekForward))
        self._rewindButton.clicked.connect(self._onRewindClick)
        self._forwardButton.clicked.connect(self._onForwardClick)

    def _configureLayout(self):
        layout = QHBoxLayout(self)
        layout.setContentsMargins(0, 0, 0, 0)
        layout.addWidget(self._rewindButton)
        layout.addWidget(self._forwardButton)
        layout.addWidget(self._timeSlider)
        layout.addWidget(self._timerLabel)

    def _onValueChange(self, newValue: int):
        self._updateTimerLabel(newValue)

    def _onRewindClick(self):
        self._timeSlider.triggerAction(QSlider.SliderSingleStepSub)

    def _onForwardClick(self):
        self._timeSlider.triggerAction(QSlider.SliderSingleStepAdd)

    def _updateTimerLabel(self, timeStep: int):
        self._timerLabel.setText(f"{timeStep}")


if __name__ == '__main__':
    app = QApplication([])
    slider = TimeSliderWidget()
    slider.setTimeSteps(20)
    window = QMainWindow()
    window.setCentralWidget(slider)
    window.show()
    app.exec()

I also tried setValue, setSliderPosition instead of triggerAction but none of these worked.

Handle in the correct position after clicking the buttons

Handle not moving after clicking buttons