My wife has experienced this twice since we've picked up the car back in June. Essentially, while driving she gets a brake warning, noting that ABS and Regenerative braking has been disabled. (I don't have the exact wording and have asked her to take a picture the next time it happens). On the first occasion it occurred on "start up" so she rebooted the system and it went away. Last night it happened while on the highway. Regen was definitely disabled according to her report and the message was onscreen the rest of the way home. This morning, the car was back to normal. Has anyone else experienced this? Should I contact the Tesla SC? And have been on 21.9 since we picked up the car.