grist-core: Suddenly unable to access our self-hosted documents

We have self-hosted Grist since its availability on docker. One or two weeks ago, it has become impossible for us to connect to our Grist server; the error is something we had encountered at the very inception of Grist:

Something went wrong
There was an error: cannot find user.

I have changed nothing to the docker-compose.yml file:

version: "3"

services:
  grist-kuq:
    image: gristlabs/grist
    container_name: grist
    restart: unless-stopped
    volumes:
      - /home/stsinc/dkr/gsk/dta:/persist
    ports:
      - 8484:8484
    environment:
      - APP_DOC_URL=https://grist.[our-internal-domain, has not changed]
      - APP_HOME_URL=https://[our-internal-domain, has not changed]
      - DEBUG=0
      - GRIST_EXPERIMENTAL_PLUGINS=true
      - GRIST_FORWARD_AUTH_LOGOUT_PATH=/signed-out
      - GRIST_HIDE_UI_ELEMENTS=helpCenter,billing,templates,multiSite,multiAccounts
      - GRIST_HOST=0.0.0.0
      - GRIST_ORG_IN_PATH=false
      - GRIST_PAGE_TITLE_SUFFIX=_blank
      - GRIST_PROXY_AUTH_HEADER=Remote-Email
      - GRIST_SANDBOX_FLAVOR=unsandboxed
      - GRIST_SESSION_SECRET=[the secret , has not changed]
      - GRIST_SINGLE_ORG=docs
      - GRIST_SUPPORT_ANON=false
      - TYPEORM_DATABASE=[database name, has not changed]
      - TYPEORM_HOST=[the URL to the database, has not changed]
      - TYPEORM_PASSWORD=[database password, has not changed]
      - TYPEORM_PORT=5432
      - TYPEORM_TYPE=postgres
      - TYPEORM_USERNAME=docker
      - TZ=America/New_York
    labels:
      - "com.centurylinklabs.watchtower.enable=true"

# For SWAG
networks:
  default:
    name: lsio
    external: true

Here is what the container log says during the session:

Welcome to Grist.
In quiet mode, see http://localhost:8484 to use.
For full logs, re-run with DEBUG=1
Setting up database...
Database setup complete.
2023-11-30 11:18:34.847 - info: == Grist version is 1.1.8 (commit unknown)
2023-11-30 11:18:34.850 - debug: skipping incomplete language ar (set GRIST_OFFER_ALL_LANGUAGES if you want it)
2023-11-30 11:18:34.850 - debug: skipping incomplete language cs (set GRIST_OFFER_ALL_LANGUAGES if you want it)
2023-11-30 11:18:34.854 - debug: skipping incomplete language fa (set GRIST_OFFER_ALL_LANGUAGES if you want it)
2023-11-30 11:18:34.858 - debug: skipping incomplete language ja (set GRIST_OFFER_ALL_LANGUAGES if you want it)
2023-11-30 11:18:34.859 - debug: skipping incomplete language nl (set GRIST_OFFER_ALL_LANGUAGES if you want it)
2023-11-30 11:18:34.864 - debug: skipping incomplete language th (set GRIST_OFFER_ALL_LANGUAGES if you want it)
2023-11-30 11:18:34.870 - info: Loading empty config because /persist/config.json missing
2023-11-30 11:18:34.870 - warn: GRIST_PROXY_AUTH_HEADER is deprecated; interpreted as a synonym of GRIST_FORWARD_AUTH_HEADER
2023-11-30 11:18:34.887 - warn: did not find an appropriately named example workspace in deployment
2023-11-30 11:18:34.891 - info: No plugins found in directory: /grist/.grist/plugins
2023-11-30 11:18:34.895 - info: Found 2 valid plugins on the system
2023-11-30 11:18:34.895 - debug: PLUGIN builtIn/core -- /grist/plugins/core
2023-11-30 11:18:34.896 - debug: PLUGIN bundled/grist-bundled -- /grist/node_modules/@gristlabs/grist-widget/dist/plugins/grist-bundled
2023-11-30 11:18:34.899 - info: Server timeouts: keepAliveTimeout 305000 headersTimeout 306000
2023-11-30 11:18:34.901 - info: server(home,docs,static) available at 0.0.0.0:8484
2023-11-30 11:18:34.908 - warn: Failed to create GoogleAuth endpoint: GOOGLE_CLIENT_SECRET is not defined
2023-11-30 11:18:34.912 - info: Server timeouts: keepAliveTimeout 305000 headersTimeout 306000
2023-11-30 11:18:34.912 - info: pluginServer available at 0.0.0.0:45205
2023-11-30 11:18:34.913 - info: == appRoot: /grist
2023-11-30 11:18:34.913 - info: == i18:namespace: client,server
2023-11-30 11:18:34.913 - info: == docsRoot: /persist/docs
2023-11-30 11:18:34.913 - info: == defaultBaseDomain: grist.[our-domain]
2023-11-30 11:18:34.913 - info: == instanceRoot: /persist
2023-11-30 11:18:34.913 - info: == tag: unknown
2023-11-30 11:18:34.914 - info: == database: postgres://[ip of Postgres server]:5432/grist
2023-11-30 11:18:34.914 - info: == userRoot: /grist/.grist
2023-11-30 11:18:34.914 - info: == bundledRoot: /grist/node_modules/@gristlabs/grist-widget/dist
2023-11-30 11:18:34.914 - info: == loginMiddlewareComment: forward-auth
2023-11-30 11:18:34.914 - info: == docWorkerId: testDocWorkerId_8484
2023-11-30 11:18:34.914 - info: == pluginUrl: http://0.0.0.0:45205/
2023-11-30 11:18:34.914 - info: == willServePlugins: true
2023-11-30 11:18:34.914 - info: == grist.access.supportEmail: support@getgrist.com [default] [GRIST_SUPPORT_EMAIL]
2023-11-30 11:18:34.914 - info: == grist.access.listPublicSites: false [default] [GRIST_LIST_PUBLIC_SITES]
2023-11-30 11:18:34.914 - info: == grist.integrations.sql.timeout: 1000 [default] [GRIST_SQL_TIMEOUT_MSEC]
2023-11-30 11:18:34.914 - info: == grist.integrations.allowedWebhookDomains: - [ALLOWED_WEBHOOK_DOMAINS]
2023-11-30 11:18:34.914 - info: == grist.integrations.proxy: - [GRIST_HTTPS_PROXY]
2023-11-30 11:18:34.914 - info: == grist.locale.offerAllLanguages: - [GRIST_OFFER_ALL_LANGUAGES]
2023-11-30 11:18:34.914 - info: == grist.login.system.forwardAuth.header: Remote-Email [GRIST_PROXY_AUTH_HEADER]
2023-11-30 11:18:34.914 - info: == grist.login.system.forwardAuth.active: true
2023-11-30 11:18:34.914 - info: == grist.login.system.forwardAuth.logoutPath: /signed-out [GRIST_FORWARD_AUTH_LOGOUT_PATH]
2023-11-30 11:18:34.914 - info: == grist.login.system.forwardAuth.loginPath: /auth/login [default] [GRIST_FORWARD_AUTH_LOGIN_PATH]
2023-11-30 11:18:34.914 - info: == grist.login.skipSession: - [GRIST_IGNORE_SESSION]
2023-11-30 11:18:34.914 - info: == grist.login.forced: - [GRIST_FORCE_LOGIN]
2023-11-30 11:18:34.914 - info: == grist.externalStorage.minio.bucket: - [GRIST_DOCS_MINIO_BUCKET]
2023-11-30 11:18:34.914 - info: == grist.externalStorage.disable: - [GRIST_DISABLE_S3]
2023-11-30 11:18:34.914 - info: == grist.externalStorage.active: false
2023-11-30 11:18:34.915 - info: activity docCount=15, orgCount=1, orgInGoodStandingCount=1, userCount=6, userWithLoginCount=6
2023-11-30 11:19:26.739 - debug: Auth[GET]: grist.[our-domain] / customHostSession=, method=GET, host=grist.[our-domain], path=/, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:26.861 - debug: Auth[GET]: grist.[our-domain] / customHostSession=, method=GET, host=grist.[our-domain], path=/, org=docs, email=anon@getgrist.com, userId=1, altSessionId=wxcyoLWymz7fKJ8hnVricQ
2023-11-30 11:19:26.873 - debug: Auth[GET]: grist.[our-domain] /session/access/active customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/active, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:26.877 - debug: Auth[GET]: grist.[our-domain] /session/access/all customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/all, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:26.929 - debug: Auth[GET]: grist.[our-domain] /orgs/0/workspaces customHostSession=, method=GET, host=grist.[our-domain], path=/orgs/0/workspaces, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:31.016 - debug: Auth[GET]: grist.[our-domain] /session/access/all customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/all, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:31.028 - debug: Auth[GET]: grist.[our-domain] /session/access/active customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/active, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:32.973 - debug: Auth[GET]: grist.[our-domain] / customHostSession=, method=GET, host=grist.[our-domain], path=/, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:33.050 - debug: Auth[GET]: grist.[our-domain] /session/access/all customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/all, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:33.052 - debug: Auth[GET]: grist.[our-domain] /session/access/active customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/active, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:19:33.088 - debug: Auth[GET]: grist.[our-domain] /orgs/0/workspaces customHostSession=, method=GET, host=grist.[our-domain], path=/orgs/0/workspaces, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:42.445 - debug: Auth[GET]: grist.[our-domain] /welcome/home customHostSession=, method=GET, host=grist.[our-domain], path=/welcome/home, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:42.466 - debug: Auth[GET]: grist.[our-domain] / customHostSession=, method=GET, host=grist.[our-domain], path=/, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:42.566 - debug: Auth[GET]: grist.[our-domain] /session/access/all customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/all, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:42.569 - debug: Auth[GET]: grist.[our-domain] /session/access/active customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/active, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:42.614 - debug: Auth[GET]: grist.[our-domain] /orgs/0/workspaces customHostSession=, method=GET, host=grist.[our-domain], path=/orgs/0/workspaces, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:57.164 - debug: Auth[GET]: grist.[our-domain] /session/access/all customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/all, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]
2023-11-30 11:20:57.173 - debug: Auth[GET]: grist.[our-domain] /session/access/active customHostSession=, method=GET, host=grist.[our-domain], path=/session/access/active, org=docs, email=anon@getgrist.com, userId=1, altSessionId=[session ID]

What have I done wrong or is it a regression?