I'm not asking for myself here, but has anyone any ideas about what on earth might be happening if, when you play Heardles* you get different tunes on different browsers/devices and they only sync if you repeatedly clear the cookies? It just sounds like the most extraordinary hassle, and huge puzzle.
*It's an online game that plays a short burst of a song which you have 6 goes to guess. There are different decades and themes.
I've had this before, and yes, I think it largely depends on the cookies, as the game 'remembers' the last one you played.
But they have to do this repeatedly, and well after the next game has refreshed/switched to the next one.