Please find attached example to reproduce the bug.

I have two comboboxes, one refreshing the other, and the other has some greyed-out items.
I also have an event filter declared (doing nothing).

My main program is:

import sys
from PySide2.QtWidgets import QApplication
from dialog import Dialog

class App(QApplication):
    
    def }}{{{}__{}init__{}(self, sys_argv):
        super(App, self).__{}init__{}(sys_argv)
        self.main_view = Dialog()
        self.main_view.show()
        
    def eventFilter(self, obj, event):
        return super(App, self).eventFilter(obj, event)
        
if }}{{{}__{}name__ {}{}== "__{}main__{}":
    app = App(sys.argv)
    app.installEventFilter(app)
    sys.exit(app.exec_())

Code of my Dialog is:

from PySide2.QtWidgets import QDialog
from dialog_ui import Ui_Dialog

class Dialog(QDialog):
        
    def }}{{{}__i{}nit__{}(self):
        super().__{}init__({})
        self._ui = Ui_Dialog()
        self._ui.setupUi(self)
        self._ui.comboBox1.currentIndexChanged.connect(self.comboBox1_indexChanged_slot)
 
    def comboBox1_indexChanged_slot(self, index):
        self._ui.comboBox2.clear()
        skip = False
        for index in range(100):
            self._ui.comboBox2.addItem(f"{index}")
            if skip:
                self._ui.comboBox2.model().item(index).setEnabled(False)
            skip = not skip

and code of the form is:

from PySide2.QtCore import *
from PySide2.QtGui import *
from PySide2.QtWidgets import *

class Ui_Dialog(object):
    def setupUi(self, Dialog):
        self.horizontalLayout = QHBoxLayout(Dialog)
        self.comboBox1 = QComboBox(Dialog)
        self.comboBox1.setObjectName(u"comboBox1")
        self.comboBox1.addItem("element1")
        self.comboBox1.addItem("element2")
        self.horizontalLayout.addWidget(self.comboBox1)
        self.comboBox2 = QComboBox(Dialog)
        self.comboBox2.setObjectName(u"comboBox2")
        self.horizontalLayout.addWidget(self.comboBox2)

        QMetaObject.connectSlotsByName(Dialog)

The Dialog form only contains the two combo boxes, first one with 2 items (code generated by pyqt).

I see a strange behaviour: after several alternative changes on the two combo boxes, I have this:

Traceback (most recent call last):
  File "./bug_combo_box.py", line 13, in eventFilter
    return super(App, self).eventFilter(obj, event)
TypeError: 'PySide2.QtCore.QObject.eventFilter' called with wrong argument types:
  PySide2.QtCore.QObject.eventFilter(Dialog, QStandardItem)
Supported signatures:
  PySide2.QtCore.QObject.eventFilter(PySide2.QtCore.QObject, PySide2.QtCore.QEvent)

What is happening? Memory corruption? What is strange is that it is always the same error, with only first parameter (here, `Dialog`, which is my main QDialog) changed (I have seen also App or QFrame).
Second parameter is always a `QStandardItem`, which has no sense (only events inheriting from QEvent expected here).

If I remove the `self._ui.comboBox2.model().item(index).setEnabled(False)` line, no more bug.
If I remove the event filter, no more bug.

What is wrong?

Please find attached example to reproduce the bug.