[Python] Tkinter, Click Box frame Changing colour when I click, and no "cross" appears

I'm almost done on my project but i'm stuck on something... I've created a clickbox in order to show/make disappear password. Everything is working fine appart of the coulour theme part. When i click on the box the default grey appears and no cross in the box appears. When i maintain my mouse click i can see the defaults grey and the cross appears. But as soon as i release my mouse click the right coulour comes back bu the cross disappears.... Excuse me for my english, i'm french and this problem is quite difficult to explain....

here is my code and photos so you can understand....

Color Theme issue

# AUTHENTIFICATION Info ##########################################################################
authentification_frame = tkinter.LabelFrame(frame, text="Authentification", fg="white")
authentification_frame.grid(row=0, column=0, sticky="news", padx=20, pady=10)
authentification_frame.configure(background="#A0522D")

identifiant_label = tkinter.Label(authentification_frame, text="Identifiant", fg="white")
identifiant_label.grid(row=0, column=0)
identifiant_label.configure(background="#A0522D")

mdp_label = tkinter.Label(authentification_frame, text="Mot de passe", fg="white")
mdp_label.grid(row=0, column=1)
mdp_label.configure(background="#A0522D")

identifiant_entry = tkinter.Entry(authentification_frame, justify='center', width=25)
identifiant_entry.insert(0, "******")
mdp_entry = tkinter.Entry(authentification_frame, show='*', justify='center', width=25)
identifiant_entry.grid(row=1, column=0)
mdp_entry.insert(0, "******")
mdp_entry.grid(row=1, column=1)


#SHOW PASSWORD#############################################################################

def show_password():
if mdp_entry.cget('show') == '':
mdp_entry.config(show='*')
check_button.config(text='Afficher mot de passe')
else:
mdp_entry.config(show='')
check_button.config(text='Masquer mot de passe')


check_button=tkinter.Checkbutton(authentification_frame, text="Afficher mot de passe", fg="white", command=show_password)
check_button.grid(row=3, column=1)
check_button.configure(background="#A0522D")


for widget in authentification_frame.winfo_children():
widget.grid_configure(padx=10, pady=5)

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