为什么过一段时间我的tkinter顶层会冻结?

我的主窗口和顶层都有秒表。一旦程序启动,手表就会启动,并通过关闭程序停止。使用按钮启动顶层。顶层应该显示秒表的副本。但是,当我打开顶层超过一个小时,它就会冻结。主窗口运行正常。当我手动关闭并重新打开它时,顶层可以再工作一个小时左右。有人知道可能是什么问题吗?我在Windows操作系统上运行代码。

相关代码如下:

import datetime
import time
import tkinter as tk

time_elapse_flag = False
start_time = datetime.datetime.now()
diff = 0

def time_elapse():
    global time_elapse_flag
    global diff

    if(not time_elapse_flag):      
            time_elapse_flag = True
            time_elapse_count = tk.Label(window, text='', relief='sunken', bg='white', font='Helvetica 16 bold')
            time_elapse_count.place(x=10, y=150, width=200, height=50)
            start_time = datetime.datetime.now().replace(microsecond=0)

            time_elapse_label = tk.Label(window, text='Recording data since:', font='Helvetica 12 bold')
            time_elapse_label.place(x=10, y=120, width=200, height=30)

            def update_time():
                global start_time
                global diff
                current_time = datetime.datetime.now().replace(microsecond=0)
                diff = current_time - start_time
                time_elapse_count.config(text=diff)
                time_elapse_label.after(1000,update_time)

            update_time()

    else:
        time_elapse_flag = False
        time_elapse_count = tk.Label(window, text='')
        time_elapse_count.place(x=10, y=150, width=200, height=50)

        time_elapse_label = tk.Label(window, text='')
        time_elapse_label.place(x=10, y=120, width=200, height=30)

def Param_Window():   
    global time_elapse_flag
    global diff

    pw = tk.Toplevel()
    pw.geometry('1200x550') 

    def update_values():
        global diff

        if(time_elapse_flag):
                time_elapse_label = tk.Label(pw, text='Recording data since:', font='Helvetica 20 bold')
                time_elapse_count = tk.Label(pw, text=diff, relief='sunken', bg='white', font='Helvetica 16 bold')
                time_elapse_label.place(x=640, y=350, width=300, height=50)
                time_elapse_count.place(x=640, y=400, width=200, height=50)
        else:
                time_elapse_label = tk.Label(pw, text='')
                time_elapse_count = tk.Label(pw, text='')
                time_elapse_label.place(x=640, y=350, width=300, height=50)
                time_elapse_count.place(x=640, y=400, width=200, height=50)

        pw.after(800,update_values)

    update_values()

if __name__ == "__main__":
    window = tk.Tk()
    window.geometry('550x250')

    disp_param_button = tk.Button(window, text='Display Parameters', command=Param_Window, bg='sky blue', font='Helvetica 12 bold', width=20, state='normal', relief='raised')
    disp_param_button.place(x=300, y=150)
    print('Automatically starting in')

    for cd in range(5):
        print(5-cd)
        time.sleep(1)

    time_elapse()

    window.mainloop( )