Problems visualizing mesh after importing and meshing a step file with netgengui

Hello,

I have a problem with the Netgen.gui() when importing and meshing a step file. I can import the geometry with OCCGeometry() and generate the mesh with GenerateMesh(), but when I use netgen.gui to look at the mesh and geometry, I can't see the mesh, only the geometry. If I use "Generate Mesh" from netgen.gui(), then the mesh is shown to me normally.

I also tested this with the webgui in a jupyternotebook and there are no problems. I am able to draw the mesh without any issues. 

The question is if it is a bug of the netgen.gui, because it works fine with the webgui, or do I do something wrong when creating geometry, mesh and Draw(mesh)?

Here is a minimal example where I use the netgen.gui which is called from a tkinter app:


import tkinter as tk
from tkinter import ttk


root = tk.Tk()
root.geometry("500x500+400+400")

main_frame = tk.Frame(master=root)
main_frame.pack(fill="both", expand=True)

button = ttk.Button(master=main_frame, command=lambda: mesh_and_draw(), text="netgen.gui")
button.pack(pady=200)

def mesh_and_draw():

    import netgen.occ
    
    geo = netgen.occ.OCCGeometry('path_to_file/file.stp')
    mesh = geo.GenerateMesh(maxh=2.0)

    from ngsolve import Draw, Mesh
    mesh_ = Mesh(mesh)
    Draw(mesh_)


    import netgen.gui

root.mainloop()


Here is a minimal example where I use the webgui:

import netgen.occ
from ngsolve import Mesh
from ngsolve.webgui import Draw

geo = netgen.occ.OCCGeometry('path_to_file/file.stp')
mesh = geo.GenerateMesh(maxh=2.0)

Draw(Mesh(mesh))



I hope someone can say something about this and thanks in advance.

Greetings 
Hagen