``session_redis`` is not compatible with ``auth_session_timeout``.
``session_redis`` overrides property ``odoo.http.Application.session_store`` by returning a ``RedisSessionStore`` object instead of a ``odoo.http.FilesystemSessionStore`` object.
``auth_session_timeout`` expects ``odoo.http.Application.session_store`` object to define method ``get_session_filename()``, which does not exist for ``RedisSessionStore`` objects.
This results in an ``AttributeError`` that prevents user authentication, and Odoo becomes inaccessible.
SilvioC2C