Invalid Start Byte when trying to route to Dash App from Flask

Dash Python
1 
from flask import Blueprint, Flask, jsonify, redirect, render_template_string, url_for
from flask_oidc import OpenIDConnect
from okta import UsersClient
import dash

oidc = OpenIDConnect()
okta_client = UsersClient("https://dev-XXXXXX.okta.com",
            "somesecret")

app = Flask(__name__)

app.config.from_mapping(
SECRET_KEY="testkey",
OIDC_CLIENT_SECRETS="/app/appname/client_secrets.json",
OIDC_COOKIE_SECURE= False,
OIDC_CALLBACK_ROUTE="/oidc/callback",
OIDC_SCOPES=["openid", "email", "profile"],
OIDC_ID_TOKEN_COOKIE_NAME="oidc_token",
DEBUG_TB_INTERCEPT_REDIRECTS = False)

oidc.init_app(app)

dash_app.layout = layout.layout
callbacks.register_dash_callbacks(dash_app)
dash_app.run_server(debug=True)

@app.route("/" , methods=["GET"])
@oidc.require_login
def redirect_to_app():
    return redirect(url_for(dash_app.config.requests_pathname_prefix))

gives me the following:

UnicodeDecodeError: 'utf-8' codec can't decode byte 0x8b in position 1: invalid start byte

The app works just fine and integrates well into the Flask app. I’ve tried researching but wasn’t able to find anything useful.

I could also get it to work by separating it out into a blueprint like so:

home_blueprint = Blueprint("home", __name__, url_prefix="/")
@home_blueprint.route("/" , methods=["GET"])
@oidc.require_login
def index():
    return redirect(url_for('/dash/'))

But then accessing the app directly via localhost:5000/dash/ was still possible without authorization.

Thank you in advance for your help.
Here the complete traceback:

Traceback (most recent call last):
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/vendor/wrapt/wrappers.py", line 602, in __call__
    return self._self_wrapper(self.__wrapped__, self._self_instance,
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/helpers.py", line 20, in wrapper
    return func(pin, wrapped, instance, args, kwargs)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/patch.py", line 331, in traced_wsgi_app
    return wrapped(environ, start_response)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/vendor/wrapt/wrappers.py", line 602, in __call__
    return self._self_wrapper(self.__wrapped__, self._self_instance,
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/helpers.py", line 20, in wrapper
    return func(pin, wrapped, instance, args, kwargs)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/helpers.py", line 29, in wrapper
    return wrapped(*args, **kwargs)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 1816, in full_dispatch_request
    return self.finalize_request(rv)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 1833, in finalize_request
    response = self.process_response(response)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/vendor/wrapt/wrappers.py", line 602, in __call__
    return self._self_wrapper(self.__wrapped__, self._self_instance,
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/helpers.py", line 20, in wrapper
    return func(pin, wrapped, instance, args, kwargs)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/helpers.py", line 29, in wrapper
    return wrapped(*args, **kwargs)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask/app.py", line 2112, in process_response
    response = handler(response)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/vendor/wrapt/wrappers.py", line 554, in __call__
    return self._self_wrapper(self.__wrapped__, instance,
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/ddtrace/contrib/flask/wrappers.py", line 23, in trace_func
    return wrapped(*args, **kwargs)
  File "/pyenv/versions/3.8.0/envs/customer-feedback-hub/lib/python3.8/site-packages/flask_debugtoolbar/__init__.py", line 202, in process_response
    response_html = response.data.decode(response.charset)