Okay, this has happened twice, and both times in a left hand sweeper turn. There's a 'bump' in the rear as if running over a plastic bottle. It's a momentary jerk with no noise associated. But very disconcerting. When it happened at 60+, the car 'stepped' to the side a few inches. I haven't found any indication of this momentary jerk on any Porsche forums, but on some Mercedes forums, the same symptom has been mentioned as indicating a "valve body repair" was needed. Very vague stuff, however.

I'll get it to the shop in a few days to check fluid level, but I'm wondering if anyone else has experienced this?