The application called an interface that was marshalled for a different thread error

Question

I am writing a code to compare two parts in catia. I used win32com.client to read the document. I am also using threading to run the progress bar. for some reason, I am getting below error even though I have defined document_new as global.
Error:

Exception in thread Thread-22:
Traceback (most recent call last):
  File "D:\VirtualEnv\env\lib\threading.py", line 926, in _bootstrap_inner
    self.run()
  File "D:\VirtualEnv\env\lib\threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\as11114\AppData\Local\Temp\ipykernel_16240\2501566542.py", line 62, in STD_Compare
    if document_old == document_new:
  File "D:\VirtualEnv\env\lib\site-packages\win32com\client\dynamic.py", line 290, in __eq__
    return self._oleobj_ == other
pywintypes.com_error: (-2147417842, 'The application called an interface that was marshalled for a different thread.', None, None)

Here is the code. Method STD_Check in class will first read one document and method STD_Compare will then read next document. If both documents are same then user gets a message that both documents are same.

import os
import win32com.client
import numpy as np
import pandas as pd
import openpyxl
import threading
from tkinter import *
from tkinter import ttk
from tkinter import messagebox
# import pythoncom to enable 'win32com.client.Dispatch' in Threads
import pythoncom
# import psutil to check whether any application is open or not, in this case checking Catia
import psutil

class STD_Check_compare():
    
    def __init__(self):
        #Form    
        self.root = Tk()
        self.root.geometry("700x200")
        self.root.title("STD Check")
        self.mainframe = ttk.Frame(self.root, padding="3 3 12 12")
        self.mainframe.grid(column=0, row=0, sticky=(N, W, E, S))
        self.root.columnconfigure(0, weight=1)
        self.root.rowconfigure(0, weight=1)
#==========================================================================================================
    def STD_Check(self):
        
        self.STD_Check_button["state"] = "disable"
        
        global document_new # defined as global
        
        pythoncom.CoInitialize() # to enable 'win32com.client.Dispatch' in Threads
        Cat = win32com.client.Dispatch('catia.application')
        Cat.Visible = True
        Cat.DisplayFileAlerts = True
        document_new = Cat.ActiveDocument  #calling the active document

        self.progressbar_STDCheck.start()
        #Do something

        self.progressbar_STDCheck.stop()
        messagebox.showinfo("", "STD Check done for parameters. Excel created and stored in defined folder")
        self.STD_Check_button["state"] = "normal"


    def STD_Compare(self):
        
        self.STD_Compare_button["state"] = "disable"
        
        pythoncom.CoInitialize()
        Cat = win32com.client.Dispatch('catia.application')
        Cat.Visible = True
        Cat.DisplayFileAlerts = True

        document_old = Cat.ActiveDocument

        if document_old == document_new:
            messagebox.showinfo("", "You have selected same STD file. Select old STD to compare")
            self.STD_Compare_button["state"] = "normal"
            return

        self.progressbar_STDCompare.start()
        #do something

        self.progressbar_STDCompare.stop()
        messagebox.showinfo("", "STD Comparison done in DMU")
        self.STD_Compare_button["state"] = "normal"
         

    def Thread_STD_Check(self):
        threading.Thread(target=self.STD_Check, daemon=True).start() # Calling STD_Check method
        
    def Thread_STD_Compare(self):
        threading.Thread(target=self.STD_Compare, daemon=True).start() # Calling STD_Compare method
    
    #---------------Buttons, labels and Progress bars in Frame--------------------------
    def display(self):
        #Create Label "Enter path"
        self.Label_path = ttk.Label(self.mainframe, text="Enter path to store Excel files").grid(column=1, row=3, sticky=W)
        #Create Entrybox for Enter path
        self.storepath = StringVar()
        self.path_entry = ttk.Entry(self.mainframe, width=50, textvariable = self.storepath)
        self.path_entry.grid(column=1, row=4, sticky=W)

        #Create Label "STD Check"
        self.Label1 = ttk.Label(self.mainframe, text="Press submit button for STD Check").grid(column=1, row=7, sticky=W)
        #Create Submit Button for STD Check (Call thread for STD Check)
        self.STD_Check_button = ttk.Button(self.mainframe, text="Submit", command=self.Thread_STD_Check) #to check STD
        self.STD_Check_button.grid(column=2, row=7, sticky=W)

        #Create Label "STD Compare"
        self.Label2 = ttk.Label(self.mainframe, text="Press submit button to compare STD").grid(column=1, row=10, sticky=W)
        #Create Submit Button for STD Comparison(Call thread for STD Comparison)
        self.STD_Compare_button = ttk.Button(self.mainframe, text="Submit", command=self.Thread_STD_Compare) #to compare STD
        self.STD_Compare_button.grid(column=2, row=10, sticky=W)
        
        self.progressbar_STDCheck = ttk.Progressbar(self.mainframe, style='text.Horizontal.TProgressbar', mode='indeterminate', length=150)
        self.progressbar_STDCheck.grid(column = 3, row = 7)

        self.progressbar_STDCompare = ttk.Progressbar(self.mainframe, style='text.Horizontal.TProgressbar', mode='indeterminate', length=150)
        self.progressbar_STDCompare.grid(column = 3, row = 10)
        
        
        self.root.mainloop()
    
start = STD_Check_compare()
start.display()