PyQt5 - Issue with using QSettings to save and restore widget settings

app_main.py

import os, sys, time, traceback

from PyQt5 import QtWidgets, uic, QtCore, QtGui
from PyQt5.QtCore import QFileInfo, QSettings
from PyQt5.QtWidgets import qApp

from ui_mainwindow import Ui_MainWindow

def settings_value_is_valid(val):
    # https://stackoverflow.com/a/60028282/4988010
    if isinstance(val, QtGui.QPixmap):
        return not val.isNull()
    return True


def settings_restore(settings):
    # https://stackoverflow.com/a/60028282/4988010
    finfo = QtCore.QFileInfo(settings.fileName())

    if finfo.exists() and finfo.isFile():
        for w in QtWidgets.qApp.allWidgets():
            if w.objectName():
                mo = w.metaObject()
                for i in range(mo.propertyCount()):
                    prop = mo.property(i)
                    name = prop.name()
                    last_value = w.property(name)
                    key = "{}/{}".format(w.objectName(), name)
                    # print(prop, name, last_value, key)
                    if not settings.contains(key):
                        continue
                    val = settings.value(key, type=type(last_value),)
                    if (
                        val != last_value
                        and settings_value_is_valid(val)
                        and prop.isValid()
                        and prop.isWritable()
                    ):
                        w.setProperty(name, val)


def settings_save(settings):
    # https://stackoverflow.com/a/60028282/4988010
    for w in QtWidgets.qApp.allWidgets():
        if w.objectName():
            mo = w.metaObject()
            for i in range(mo.propertyCount()):
                prop = mo.property(i)
                name = prop.name()
                key = "{}/{}".format(w.objectName(), name)
                val = w.property(name)
                if settings_value_is_valid(val) and prop.isValid() and prop.isWritable():
                    settings.setValue(key, w.property(name))

class MyApp(QtWidgets.QMainWindow):
    
    def __init__(self):
        super(MyApp, self).__init__()
        
        self.settings = QSettings("./temp/gui_settings.ini", QSettings.IniFormat)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)


        self.ui.action_config_save_current_values.triggered.connect(self.config_widgets_save_settings)
        self.ui.action_config_load_config_file.triggered.connect(self.config_widgets_load_settings)
        self.ui.action_config_reset_to_factory_default.triggered.connect(self.config_widgets_reset_settings)

    def config_widgets_save_settings(self):
        # Save settings 
        # self.logger.info('Saving current values of the widgets into a config file.')
        settings_save(self.settings)

    def config_widgets_load_settings(self):
        # self.logger.info('Loading saved widgets settings config file.')
        # Load previous usage settings 
        settings_restore(self.settings)

    def config_widgets_reset_settings(self):
        # self.logger.info('Resetting the saved widgets settings config file to default factor settings.')
        self.settings.clear()
        self.ui.setupUi(self)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    # print(QtWidgets.QStyleFactory.keys())
    app.setStyle('Fusion')
    window = MyApp()
    window.show()
    app.exec_()
    # sys.exit(app.exec_())

main.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>368</width>
    <height>204</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QPushButton" name="start_button">
    <property name="geometry">
     <rect>
      <x>100</x>
      <y>80</y>
      <width>109</width>
      <height>23</height>
     </rect>
    </property>
    <property name="styleSheet">
     <string notr="true">QPushButton::checked {background-color: #6cf090; }</string>
    </property>
    <property name="text">
     <string>Start</string>
    </property>
    <property name="checkable">
     <bool>false</bool>
    </property>
   </widget>
   <widget class="QWidget" name="layoutWidget">
    <property name="geometry">
     <rect>
      <x>10</x>
      <y>10</y>
      <width>342</width>
      <height>51</height>
     </rect>
    </property>
    <layout class="QGridLayout" name="gridLayout_2">
     <item row="0" column="0">
      <widget class="QLabel" name="label_10">
       <property name="text">
        <string>Param A</string>
       </property>
      </widget>
     </item>
     <item row="0" column="2">
      <widget class="QLabel" name="label_12">
       <property name="text">
        <string>Param C</string>
       </property>
      </widget>
     </item>
     <item row="0" column="1">
      <widget class="QLabel" name="label_11">
       <property name="text">
        <string>Param B</string>
       </property>
      </widget>
     </item>
     <item row="1" column="2">
      <widget class="QDoubleSpinBox" name="param_c">
       <property name="decimals">
        <number>3</number>
       </property>
       <property name="maximum">
        <double>100000000.000000000000000</double>
       </property>
       <property name="value">
        <double>1234.000000000000000</double>
       </property>
      </widget>
     </item>
     <item row="1" column="0">
      <widget class="QDoubleSpinBox" name="param_a">
       <property name="decimals">
        <number>3</number>
       </property>
       <property name="maximum">
        <double>9999.000000000000000</double>
       </property>
       <property name="singleStep">
        <double>0.050000000000000</double>
       </property>
       <property name="value">
        <double>1.500000000000000</double>
       </property>
      </widget>
     </item>
     <item row="1" column="1">
      <widget class="QDoubleSpinBox" name="param_b">
       <property name="decimals">
        <number>3</number>
       </property>
       <property name="maximum">
        <double>9999.000000000000000</double>
       </property>
       <property name="singleStep">
        <double>0.050000000000000</double>
       </property>
       <property name="value">
        <double>0.250000000000000</double>
       </property>
      </widget>
     </item>
     <item row="0" column="3">
      <widget class="QLabel" name="label_4">
       <property name="text">
        <string>Param D</string>
       </property>
      </widget>
     </item>
     <item row="1" column="3">
      <widget class="QSpinBox" name="param_d">
       <property name="maximum">
        <number>999999999</number>
       </property>
       <property name="value">
        <number>456</number>
       </property>
      </widget>
     </item>
    </layout>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>368</width>
     <height>21</height>
    </rect>
   </property>
   <widget class="QMenu" name="menuFile">
    <property name="title">
     <string>File</string>
    </property>
    <widget class="QMenu" name="menuWidget_defaults">
     <property name="title">
      <string>Widget defaults</string>
     </property>
     <addaction name="action_config_save_current_values"/>
     <addaction name="action_config_load_config_file"/>
     <addaction name="action_config_reset_to_factory_default"/>
    </widget>
    <addaction name="menuWidget_defaults"/>
   </widget>
   <addaction name="menuFile"/>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
  <action name="action_config_save_current_values">
   <property name="text">
    <string>Save current values</string>
   </property>
  </action>
  <action name="action_config_load_config_file">
   <property name="text">
    <string>Load config file</string>
   </property>
  </action>
  <action name="action_config_reset_to_factory_default">
   <property name="text">
    <string>Reset to factory default</string>
   </property>
  </action>
 </widget>
 <resources/>
 <connections/>
</ui>

ui_mainwindow.py

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file 'main.ui'
#
# Created by: PyQt5 UI code generator 5.15.0
#
# WARNING: Any manual changes made to this file will be lost when pyuic5 is
# run again.  Do not edit this file unless you know what you are doing.


from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(368, 204)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.start_button = QtWidgets.QPushButton(self.centralwidget)
        self.start_button.setGeometry(QtCore.QRect(100, 80, 109, 23))
        self.start_button.setStyleSheet("QPushButton::checked {background-color: #6cf090; }")
        self.start_button.setCheckable(False)
        self.start_button.setObjectName("start_button")
        self.layoutWidget = QtWidgets.QWidget(self.centralwidget)
        self.layoutWidget.setGeometry(QtCore.QRect(10, 10, 342, 51))
        self.layoutWidget.setObjectName("layoutWidget")
        self.gridLayout_2 = QtWidgets.QGridLayout(self.layoutWidget)
        self.gridLayout_2.setContentsMargins(0, 0, 0, 0)
        self.gridLayout_2.setObjectName("gridLayout_2")
        self.label_10 = QtWidgets.QLabel(self.layoutWidget)
        self.label_10.setObjectName("label_10")
        self.gridLayout_2.addWidget(self.label_10, 0, 0, 1, 1)
        self.label_12 = QtWidgets.QLabel(self.layoutWidget)
        self.label_12.setObjectName("label_12")
        self.gridLayout_2.addWidget(self.label_12, 0, 2, 1, 1)
        self.label_11 = QtWidgets.QLabel(self.layoutWidget)
        self.label_11.setObjectName("label_11")
        self.gridLayout_2.addWidget(self.label_11, 0, 1, 1, 1)
        self.param_c = QtWidgets.QDoubleSpinBox(self.layoutWidget)
        self.param_c.setDecimals(3)
        self.param_c.setMaximum(100000000.0)
        self.param_c.setProperty("value", 1234.0)
        self.param_c.setObjectName("param_c")
        self.gridLayout_2.addWidget(self.param_c, 1, 2, 1, 1)
        self.param_a = QtWidgets.QDoubleSpinBox(self.layoutWidget)
        self.param_a.setDecimals(3)
        self.param_a.setMaximum(9999.0)
        self.param_a.setSingleStep(0.05)
        self.param_a.setProperty("value", 1.5)
        self.param_a.setObjectName("param_a")
        self.gridLayout_2.addWidget(self.param_a, 1, 0, 1, 1)
        self.param_b = QtWidgets.QDoubleSpinBox(self.layoutWidget)
        self.param_b.setDecimals(3)
        self.param_b.setMaximum(9999.0)
        self.param_b.setSingleStep(0.05)
        self.param_b.setProperty("value", 0.25)
        self.param_b.setObjectName("param_b")
        self.gridLayout_2.addWidget(self.param_b, 1, 1, 1, 1)
        self.label_4 = QtWidgets.QLabel(self.layoutWidget)
        self.label_4.setObjectName("label_4")
        self.gridLayout_2.addWidget(self.label_4, 0, 3, 1, 1)
        self.param_d = QtWidgets.QSpinBox(self.layoutWidget)
        self.param_d.setMaximum(999999999)
        self.param_d.setProperty("value", 456)
        self.param_d.setObjectName("param_d")
        self.gridLayout_2.addWidget(self.param_d, 1, 3, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 368, 21))
        self.menubar.setObjectName("menubar")
        self.menuFile = QtWidgets.QMenu(self.menubar)
        self.menuFile.setObjectName("menuFile")
        self.menuWidget_defaults = QtWidgets.QMenu(self.menuFile)
        self.menuWidget_defaults.setObjectName("menuWidget_defaults")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.action_config_save_current_values = QtWidgets.QAction(MainWindow)
        self.action_config_save_current_values.setObjectName("action_config_save_current_values")
        self.action_config_load_config_file = QtWidgets.QAction(MainWindow)
        self.action_config_load_config_file.setObjectName("action_config_load_config_file")
        self.action_config_reset_to_factory_default = QtWidgets.QAction(MainWindow)
        self.action_config_reset_to_factory_default.setObjectName("action_config_reset_to_factory_default")
        self.menuWidget_defaults.addAction(self.action_config_save_current_values)
        self.menuWidget_defaults.addAction(self.action_config_load_config_file)
        self.menuWidget_defaults.addAction(self.action_config_reset_to_factory_default)
        self.menuFile.addAction(self.menuWidget_defaults.menuAction())
        self.menubar.addAction(self.menuFile.menuAction())

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.start_button.setText(_translate("MainWindow", "Start"))
        self.label_10.setText(_translate("MainWindow", "Param A"))
        self.label_12.setText(_translate("MainWindow", "Param C"))
        self.label_11.setText(_translate("MainWindow", "Param B"))
        self.label_4.setText(_translate("MainWindow", "Param D"))
        self.menuFile.setTitle(_translate("MainWindow", "File"))
        self.menuWidget_defaults.setTitle(_translate("MainWindow", "Widget defaults"))
        self.action_config_save_current_values.setText(_translate("MainWindow", "Save current values"))
        self.action_config_load_config_file.setText(_translate("MainWindow", "Load config file"))
        self.action_config_reset_to_factory_default.setText(_translate("MainWindow", "Reset to factory default"))


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())