The issue with "Stop Safely Now" (SSN) happened to me on a highway. It's scary as the car just stops. Luckily it was heavy traffic so people went around me. On an empty highway, with vehicles coming faster, it could be dangerous.
Anyway, I switched off the car, was about to call pickup service but tried again and it started.
Took it to the dealership and they installed the new software, and changed by 12V battery which was defective. That was supposed to resolve the problem.
BUT, yesterday again the same issue happened to me this time with my kids in the car. Luckily we were not too far from home. Did the same routing - stop, wait, start - and it worked. But now I am nervous like hell taking this car out. Taking to the dealership again tonight.
I love this car - have been an evangelist for this for so long, but this is turning out to be a very concerning issue. And apparently happening a lot as one case see by googling the issue.