session expire randomly with firefox, works with chrome and safari

Hi,

I'm using L5.2 (in the process of migrating to 5.3 early 2017) and we just discover an issue with sessions and firefox (tested with 49.0.1).

The session expires randomly, displaying the login form every few requests (not every single constant, not every x secs, it depends!). I don't experience the issue with Chrome nor Safari.

First thing that comes in mind is cookie related. I compared the cookies from firefox with the cookies from chrome, I didn't see anything strange (expires 2 hours later, as per my config, domain is correct, path is '/', etc).

If I use the "remember me" feature from my login forms, then I don't have any disconnection and the new cookie (the one created by the fact that I use this feature) is accessed at random times, on random pages. (which makes me think that it is def cookie related)

Here is my session.php:

<?php

return [

    /*
    |--------------------------------------------------------------------------
    | Default Session Driver
    |--------------------------------------------------------------------------
    |
    | This option controls the default session "driver" that will be used on
    | requests. By default, we will use the lightweight native driver but
    | you may specify any of the other wonderful drivers provided here.
    |
    | Supported: "file", "cookie", "database", "apc",
    |            "memcached", "redis", "array"
    |
    */

    'driver' => env('SESSION_DRIVER', 'file'),

    /*
    |--------------------------------------------------------------------------
    | Session Lifetime
    |--------------------------------------------------------------------------
    |
    | Here you may specify the number of minutes that you wish the session
    | to be allowed to remain idle before it expires. If you want them
    | to immediately expire on the browser closing, set that option.
    |
    */

    'lifetime' => 120,

    'expire_on_close' => false,

    /*
    |--------------------------------------------------------------------------
    | Session Encryption
    |--------------------------------------------------------------------------
    |
    | This option allows you to easily specify that all of your session data
    | should be encrypted before it is stored. All encryption will be run
    | automatically by Laravel and you can use the Session like normal.
    |
    */

    'encrypt' => false,

    /*
    |--------------------------------------------------------------------------
    | Session File Location
    |--------------------------------------------------------------------------
    |
    | When using the native session driver, we need a location where session
    | files may be stored. A default has been set for you but a different
    | location may be specified. This is only needed for file sessions.
    |
    */

    'files' => storage_path().'/framework/sessions',

    /*
    |--------------------------------------------------------------------------
    | Session Database Connection
    |--------------------------------------------------------------------------
    |
    | When using the "database" or "redis" session drivers, you may specify a
    | connection that should be used to manage these sessions. This should
    | correspond to a connection in your database configuration options.
    |
    */

    'connection' => null,

    /*
    |--------------------------------------------------------------------------
    | Session Database Table
    |--------------------------------------------------------------------------
    |
    | When using the "database" session driver, you may specify the table we
    | should use to manage the sessions. Of course, a sensible default is
    | provided for you; however, you are free to change this as needed.
    |
    */

    'table' => 'sessions',

    /*
    |--------------------------------------------------------------------------
    | Session Sweeping Lottery
    |--------------------------------------------------------------------------
    |
    | Some session drivers must manually sweep their storage location to get
    | rid of old sessions from storage. Here are the chances that it will
    | happen on a given request. By default, the odds are 2 out of 100.
    |
    */

    'lottery' => [2, 100],

    /*
    |--------------------------------------------------------------------------
    | Session Cookie Name
    |--------------------------------------------------------------------------
    |
    | Here you may change the name of the cookie used to identify a session
    | instance by ID. The name specified here will get used every time a
    | new session cookie is created by the framework for every driver.
    |
    */

    'cookie' => 'laravel_session',

    /*
    |--------------------------------------------------------------------------
    | Session Cookie Path
    |--------------------------------------------------------------------------
    |
    | The session cookie path determines the path for which the cookie will
    | be regarded as available. Typically, this will be the root path of
    | your application but you are free to change this when necessary.
    |
    */

    'path' => '/',

    /*
    |--------------------------------------------------------------------------
    | Session Cookie Domain
    |--------------------------------------------------------------------------
    |
    | Here you may change the domain of the cookie used to identify a session
    | in your application. This will determine which domains the cookie is
    | available to in your application. A sensible default has been set.
    |
    */

    'domain' => null,

    /*
    |--------------------------------------------------------------------------
    | HTTPS Only Cookies
    |--------------------------------------------------------------------------
    |
    | By setting this option to true, session cookies will only be sent back
    | to the server if the browser has a HTTPS connection. This will keep
    | the cookie from being sent to you if it can not be done securely.
    |
    */

    'secure' => false,

];

I don't call the 'web' middleware directly from routes.php since I understand from RouteServiceProvider.php that all routes from Http/routes.php have now the 'web' middleware applied by default.

Nothing in laravel logs (which is not a surprise since it works with chrome).

Any idea ? thoughts ?

Thank a lot in advance