To be redundant enough to keep a car moving along, it would be insanely cost prohibitive. If Camera A fails, and it needs it to keep moving forward, does backup Camera B kick in?

You can get a decent camera sensor for $50 or less. We have different notions of what cost prohibitive means. Granted some things like LiDAR are at least currently damn expensive, but all you need is enough to make it safely to the side of the road. That's not a difficult task.

What if the "failure", doesn't impede the ability for the car to function and you are outside of cell reception in bad weather? Where if it had manual controls you could drive it to safety.

What if your car breaks down outside of cell coverage now? You seem way too intent on finding any possibility of a problem. Problems exist with everything. If it solves more problems than it creates it's a net positive though, and that doesn't seem an insurmountable bar.

Also satellite locator beacons and messengers are quite affordable, and I would expect we would see those at least on commercial vehicles.

It has to be a non nuisance. If at any point you get in the car, and it doesn't do what you want it to do in a situation that you think, well fuck I could have done that, or driven, but it couldn't, and or wouldn't allow me to, then it's "I demand a refund", or get pissed off and do something bad.

Again, you're expecting it to be perfect. You're free to make the decision to avoid the technology if you like (for as long as alternatives exist), but others will almost certainly find it good enough. There are drawbacks with email over sending a letter; there are drawbacks over driving vs. riding a horse. People accept those drawbacks in most situations because overall they make life better.

Under no circumstance will that decision always be 100% in favor of a non accident. It will happen.