KeyError: "Callback function not found for output..." on non existing output


With Dash I have created an app which is running on windows IIS (wfastcgi) on a local network with some clients. This was working fine untill I changed the app.

I removed a few components, for example a html.Div "text_input_div". After uploading the new code and preforming a iisreset command .
I am getting the following error message in the logfile:

ERROR   : 2022-03-21 19:29:35,201:         : log_exception             >>> Exception on /_dash-update-component [POST]
Traceback (most recent call last):
  File "C:\Python310\lib\site-packages\dash\", line 1297, in dispatch
    cb = self.callback_map[output]
KeyError: ''

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Python310\lib\site-packages\flask\", line 2073, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Python310\lib\site-packages\flask\", line 1518, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "C:\Python310\lib\site-packages\flask\", line 1516, in full_dispatch_request
    rv = self.dispatch_request()
  File "C:\Python310\lib\site-packages\flask\", line 1502, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File "C:\Python310\lib\site-packages\dash\", line 1335, in dispatch
    raise KeyError(msg.format(output)) from missing_callback_function
KeyError: "Callback function not found for output '', perhaps you forgot to prepend the '@'?"

Component "text_input_div" does not exist anymore, and there is no callback referring to this component.
App layout:

  • apps
  • modals
    |-- → previous file with "text_input_div" called by app1

Why do I get this error?
Is iisreset the correct way to reset the app after copying the new code to the app-folder?
Is one of the clients (the webpage is running all day) having the "text_input_div"in memory?

The app is working with no errors in the IDE.

Kind Regards