I have felt the bump too, but only post 7.0 upgrade. A day or two after I updated circumstances required me to sit in the parked car for about 1:45 with all systems running. Not only did I hear the a/c making all kinds of crazy noise (something it never did pre-update) but several times while sitting in (P)ark I felt a little bump and movement and sometimes I heard a noise from the rear. It wasn't loud or terribly obvious but I definitely wondered about it. Once it happened to me at a stop sign and I, too, wondered if I'd been rear-ended (more like tapped). I haven't felt it since then, so I'd sort of dismissed it until I read this thread. I haven't felt it in at least a week and a half. The timing of its appearance and its intermittent nature make me think it was probably introduced in an update just prior to 7.0, maybe one of those odd in-between revisions that it seems not everyone gets? Really curious what the SC had to say to those who have been in and mentioned it recently.