ExportHelper exits with exit code: 3221226356

I have a props dialog with a slider.
When the “ok” button is pressed, I want to call a “save as file selector”.
Both of them work fine on their own, unfortunately Blender crashes when I call the second in the execute method of the first.

Am I doing something wrong or is this a bug?

import bpy
from bpy_extras.io_utils import ExportHelper

class OBJECT_OT_Test(bpy.types.Operator):
bl_idname = “object.test_operator”
bl_label = “test operator”

flt_prop:  bpy.props.FloatProperty(default = 0.25, min = 0, max = 1, name='')    

def draw(self, context):
    self.layout.column().prop(self, "flt_prop", expand=True)        

def invoke(self, context, event):
    return {'RUNNING_MODAL'}

def execute(self, context):
    return {'FINISHED'}

class MENU_MT_FileBrowser(bpy.types.Operator, ExportHelper):
bl_idname = “object.file_browser”
bl_label = “test filebrowser”
filename_ext= “.blend”

def execute(self, context):
    return {'FINISHED'}

classes = (

register, unregister = bpy.utils.register_classes_factory(classes)

if name == “main”: