I don't trust Tesla's automation for one second. Of course they've also never sold a car with autonomous features, only driver assistance, and I trust their driver assistance every time I get in the car. The difference is that I am always in control of the system. I am driving. Tesla isn't. The absolute worst thing the automation is capable of doing if it screws up is to move the car a foot or so to the side before I catch it and override. And if there wasn't several feet beside the car to start with, I never would have engaged the system in the first place.
The way the system is designed, there is still a physical link between the steering wheel and the steering of the front wheels, and between the brake pedal and the brakes. The software simply cannot override that no matter what it does wrong.
If you treat it as the feature it is (a better cruise control) it's great. If you expect it to drive itself you're both ignorant, and stupid.
That said, apparently too many people were both ignorant and stupid, so in a pure marketing move, and against the law in almost every jurisdiction, Tesla retroactively removed a paid for feature from all the cars it had already sold. Luckily for me, I've rooted my car and was able to re-instate the feature that Tesla stole.
As for resisting code audits, that's partly to cover their blatant copyright infringement using GPL software without adhering to the GPL, and partly because Tesla is of the opinion that they know better than the rest of the world on all things and have a right to do anything they want to other people's property without their permission. I'd say that it will come back to bite them eventually, but as long as they have no competition, and most countries consumer protection laws lack any teeth, what incentive do they have to change?
As for Tesla's "full self driving" that's just another of a long line of marketing lies, they'll never get there with the current hardware, nor will any regulatory body ever approve it with this hardware (we don't even need to talk about software for this, the hardware is so obviously incapable of it that the software is irrelevant)