Custom window with pyqT5 under Linux

Question

I've made a program with pyQT5 on Windows which works great, but now I'm switching back to Linux and the program is buggy, when I move the window with the custom titlebar sometimes it jumps across the screen

I used this post to write the code: Custom Titlebar with frame in PyQt5

Anyone can help me

Here is a simplified sample code:

import sys
from PyQt5.QtCore import QPoint
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QApplication, QHBoxLayout, QLabel
from PyQt5.QtWidgets import QPushButton, QVBoxLayout, QWidget


class MainWindow(QWidget):

    def __init__(self):
        super(MainWindow, self).__init__()
        self.layout = QVBoxLayout()
        self.layout.addWidget(MyBar(self))
        self.setLayout(self.layout)
        self.layout.setContentsMargins(0, 0, 0, 0)
        self.layout.addStretch(-1)
        self.setMinimumSize(800, 400)
        self.setWindowFlags(Qt.FramelessWindowHint)
        self.pressing = False


class MyBar(QWidget):

    def __init__(self, parent):
        super(MyBar, self).__init__()
        self.parent = parent
        print(self.parent.width())
        self.layout = QHBoxLayout()
        self.layout.setContentsMargins(0, 0, 0, 0)
        self.title = QLabel("My Own Bar")

        btn_size = 35

        self.btn_close = QPushButton("x")
        self.btn_close.clicked.connect(self.btn_close_clicked)
        self.btn_close.setFixedSize(btn_size, btn_size)
        self.btn_close.setStyleSheet("background-color: red;")

        self.btn_min = QPushButton("-")
        self.btn_min.clicked.connect(self.btn_min_clicked)
        self.btn_min.setFixedSize(btn_size, btn_size)
        self.btn_min.setStyleSheet("background-color: gray;")

        self.btn_max = QPushButton("+")
        self.btn_max.clicked.connect(self.btn_max_clicked)
        self.btn_max.setFixedSize(btn_size, btn_size)
        self.btn_max.setStyleSheet("background-color: gray;")

        self.title.setFixedHeight(35)
        self.title.setAlignment(Qt.AlignCenter)
        self.layout.addWidget(self.title)
        self.layout.addWidget(self.btn_min)
        self.layout.addWidget(self.btn_max)
        self.layout.addWidget(self.btn_close)

        self.title.setStyleSheet("""
            background-color: black;
            color: white;
        """)
        self.setLayout(self.layout)

        self.start = QPoint(0, 0)
        self.pressing = False

    def resizeEvent(self, QResizeEvent):
        super(MyBar, self).resizeEvent(QResizeEvent)
        self.title.setFixedWidth(self.parent.width())

    def mousePressEvent(self, event):
        self.start = self.mapToGlobal(event.pos())
        self.pressing = True

    def mouseMoveEvent(self, event):
        if self.pressing:
            self.end = self.mapToGlobal(event.pos())
            self.movement = self.end-self.start
            self.parent.setGeometry(self.mapToGlobal(self.movement).x(),
                                    self.mapToGlobal(self.movement).y(),
                                    self.parent.width(),
                                    self.parent.height())
            self.start = self.end

    def mouseReleaseEvent(self, QMouseEvent):
        self.pressing = False

    def btn_close_clicked(self):
        self.parent.close()

    def btn_max_clicked(self):
        self.parent.showMaximized()

    def btn_min_clicked(self):
        self.parent.showMinimized()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec_())

I have no idea where the problem is, and I didn't test it under macOS