Strange logout issue

I've got a strange issue that I'm having a hard time nailing down.

For some reason when you check "remember me" everything is fine, however, if you DON'T check "remember me" when you login there's a strange issue. You can still login fine and you get taken to the correct page after login, and you can click anywhere on the site and the next page will load fine and you are still logged in, but the next page you try to go to you will be logged out.

As this only happens when you DON'T check "remember me", obviously there is a difference somewhere other than just saving the username and password for the next time you log in.

One thing that does seem to be happening when you login with "remember me" checked is that an additional cookie is being written with a value that looks like +0+F+AE4F4A..., but it doesn't seem that this is written when not checking "remember me".

Any ideas what the cause could be?

I solved the issue, sort of...
In application.php I changed the code to set the cookie whether you check "remember me" or not. I don't like changing core code like that but it solves the immediate issue, although I'm still unsure of what the actual root cause was.

I thought the issue was maybe being caused by something in the cb login module which is why I posted here, but as I've dug deeper into it I think it's something messing up core Joomla sessions, I just have no idea what or how.