Redis server Safari loses session upon relogin

I am using redis to store sessions on my nodejs server.

Timeline of regret:

1. On Safari, a user logs in from the homepage and creates a session

2. The user is directed to the "Successfully logged in page"

   2.a. Should a user have tried to log in with invalid credentials, s/he would not have been directed here

3. The user logs out. The session is destroyed. The user is redirected to the homepage.

4. The user tries to log in again, identically to step (1).

5. The login is validated, a session is created and then immediately lost, causing the "Successful login" page not to recognise the user as being in a session, sending him/her back to the homepage.

6. The user can now login successfully

This is puzzling, because the exact same code is being run both times. In my console logs, I get evidence of the session existing momentarily the second time around and then the next time the server processes a request, the session has been mysteriously evaporated.

Interesting things to consider: this only happens on Safari (Chrome and Firefox both let the user login every time, the session never gets erroneously destroyed) and only on even numbered login attempts.

A google search did not yield any results. Has anyone experienced this/has any clue what might be going on?

I have tried clearing cache/cookies from Safari, which does nothing.

via Uzebeckatrente