T-Junctions are the thing. No t-junctions and no roundabouts.
When that video showed up of the disapearing/teleporting cars, the real issue was traffic on a lower roundabout giving way to traffic trying to join. I got concerned and started to make noises, as I do. There was a direct reply that 't-junctions are in the game' - this surprised me a bit, as I can see them being really hard to implement, but there it is - The reply went on to say that it seemed that there was some issue wrt how t-junctions were being implemented on roundabouts, and that it would be reported to dev. I'm holding off with the concern until I see the shipped build and/or the post release bug list.