Tkinter issue regarding dynamically uncheck CheckBoxes

In Tkinter (Python) I try to dynamically uncheck a CheckBox when an another CheckBox is checked but the behavior is rather erratic.

1. If the first box is checked and i check the second one: the second box checks for few seconds then it unchecks. The event related to the second CheckBox doesn't trigger.
2. If the second box is checked and i check the first one: the behavior is correct as it uncheck the second one and check the first one. The event related to the first CheckBox does trigger.
3. If there's no single box checked and I check one box at the time the events do trigger normally.

My code :

import tkinter as tk

class App(tk.Tk):
    def __init__(self):
        super().__init__()

        self.frame = tk.Frame(self)
        self.frame.pack(fill=tk.BOTH, expand=True)

        self.entry1 = tk.Canvas(self.frame, width=100, height=100, highlightthickness=0, bd=0, bg="green", relief='solid')
        self.entry1.grid(row=0, column=0)

        self.entry2 = tk.Canvas(self.frame, width=100, height=100, highlightthickness=0, bd=0, bg="red", relief='solid')

        self.check_var1 = tk.BooleanVar()
        self.check_var1.set(True)
        self.check_box1 = tk.Checkbutton(self, text="Show Green", variable=self.check_var1, command=lambda: self.toggle_entries(self.check_var1))
        self.check_box1.pack()

        self.check_var2 = tk.BooleanVar()
        self.check_box2 = tk.Checkbutton(self, text="Show Red", variable=self.check_var2, command=lambda: self.toggle_entries(self.check_var2))
        self.check_box2.pack()

        self.check_var1.trace_add('write', self.check_var_changed)
        self.check_var2.trace_add('write', self.check_var_changed)

        self.toggle_entries(self.check_var1)

    def toggle_entries(self, var):
        if var is self.check_var1:
            if var.get():
                self.entry1.grid()
                self.entry2.grid_remove()
                self.check_var2.set(False) 
        elif var is self.check_var2:
            if var.get():
                self.entry2.grid()
                self.entry1.grid_remove()
                self.check_var1.set(False) 

    def check_var_changed(self, *args):
        if self.check_var1.get():
            self.check_var2.set(False)
        elif self.check_var2.get():
            self.check_var1.set(False)

if __name__ == "__main__":
    app = App()
    app.mainloop()

Any ideas of why this functiontoggle_entries doesn't work properly?