the-littlest-jupyterhub: login page stops working after a few days (error 500)

Bug description

After a few days without issues https://xxx.com/hub/login returns a blank page.

GET: https://xxx.com/hub/login returns 500 Internal Server Error

Response Headers

HTTP/2 500 Internal Server Error
access-control-allow-headers: accept, content-type, authorization
content-security-policy: frame-ancestors 'self'; report-uri /hub/security/csp-report
content-type: text/html
date: Fri, 06 Nov 2020 09:02:59 GMT
server: TornadoServer/6.0.4
x-jupyterhub-version: 1.1.0
content-length: 0
X-Firefox-Spdy: h2

warning in browser terminal

The character encoding of the HTML document was not declared. The document will render with garbled text in some browser configurations if the document contains characters from outside the US-ASCII range. The character encoding of the page must be declared in the document or in the transfer protocol. login

Note 1 still works for logged in user https://xxx.com/user/my-user/tree?

Note 2

The issue can be temporally fixed by restarting traefik sudo tljh-config reload proxy

Expected behaviour

jupyterhub stays available

Actual behaviour

jupyterhub stops serving the login page after a few days

How to reproduce

I don’t know how to reproduce this. I checked the logs but couldn’t find something telling. Please let me know what other infos I can provide.

Your personal set up

• OS: Ubuntu 18.04.5 LTS
• Version:

not sure how to check version but it should be a very recent one

2020-10-29 07:54:02,411 Checking if TLJH is already installed...
2020-10-29 07:54:02,412 TLJH already installed, upgrading...
2020-10-29 07:54:02,412 Upgrading TLJH installer...
2020-10-29 07:54:04,432 Upgraded pip
2020-10-29 07:54:07,848 Setup tljh package
2020-10-29 07:54:07,848 Starting TLJH installer...
2020-10-29 07:54:08,261 Setting up admin users
2020-10-29 07:54:08,275 Granting passwordless sudo to JupyterHub admins...
2020-10-29 07:54:08,275 Setting up user environment...
2020-10-29 07:54:37,971 Setting up JupyterHub...
2020-10-29 07:55:26,008 Waiting for JupyterHub to come up (1/20 tries)
2020-10-29 07:55:27,013 Waiting for JupyterHub to come up (2/20 tries)

• Configuration:

sudo tljh-config show
users:
  admin:
  - xxx
auth:
  type: nativeauthenticator.NativeAuthenticator
  NativeAuthenticator:
    minimum_password_length: 6
    check_common_password: true
    allowed_failed_logins: 3
    seconds_before_next_try: 120
https:
  enabled: true
  letsencrypt:
    email: admin+jupyterhub@xxx.io
    domains:
    - xxx.com