invalid command name "<numbers>update/check_dpi_scaling"

[ohshitgorillas]

I am creating data reduction software and the general workflow is to view a list of analysis sequences, select one, and then go to view a plot of raw data. I'm getting this cryptic error when I switch from one GUI to the next:

invalid command name "2073977167560update"
    while executing
"2073977167560update"
    ("after" script)
invalid command name "2073972183304check_dpi_scaling"
    while executing
"2073972183304check_dpi_scaling"
    ("after" script)

Here is a reproducible example:

from tkinter import ttk
import customtkinter as ctk
import matplotlib.figure as Figure
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg

def create_first_gui():
    window = ctk.CTk()
    window.title('First GUI')

    tree = ttk.Treeview(window)
    tree["columns"]=("one","two")
    tree.column("#0", width=100)
    tree.column("one", width=100)
    tree.column("two", width=100)
    tree.heading("#0",text="Column A")
    tree.heading("one", text="Column B")
    tree.heading("two", text="Column C")

    tree.insert("", 0, text="Line 1", values=("Stuff 1","Stuff 2"))

    tree.pack()

    button = ctk.CTkButton(window, text="Proceed to Second GUI", command=window.destroy)
    button.pack()

    window.mainloop()

def create_second_gui():
    window = ctk.CTk()
    window.title('Second GUI')

    fig = Figure.Figure(figsize=(5, 4))
    t = [i/100 for i in range(100)]
    fig.add_subplot(111).plot(t, [i**2 for i in t])

    canvas = FigureCanvasTkAgg(fig, master=window)
    canvas.draw()
    canvas.get_tk_widget().pack(side=ctk.TOP, fill=ctk.BOTH, expand=1)

    window.mainloop()

create_first_gui()
create_second_gui()

Am I doing something wrong? If so, what?