Rock & A Hard Place - Enterprise Rental Car Company

I'm sort of getting scammed by Enterprise rental car company. I had a car rental in May. They gave me a car that wasn't cleaned and it had a malfunction as I was entering the highway the next day. It experienced a stop/start malfunction that locked the vehicle's brakes and wheel. Due to the loss of control, I crashed into the highway entry ramp's barricade. I called the roadside assistance line and reported what happened. A California highway patrol officer stumbled upon me and stopped to help. He saw the malfunction alerts on the dash and stayed until the Enterprise-hired tow truck driver came. The tow truck driver looked at the car as well.

I discussed it at the location where they gave me a replacement car and I discussed it again at the original location where I got the original car that malfunctioned. I've called and emailed several parties, and especially over email, I've been ignored for weeks/months on end. I finally received a $5,000 bill after they went no contact without any explanation. I requested the initial malfunction report for the car and they said they'd get it to me. They sent a brakes report. I insisted again for the malfunction report, as it would show that the stop/start malfunction took place before the crash (which was out of my hands, therefore proving I'm not responsible, it was the car's failure). They said they'd get it to me a month ago.

Yesterday, I received a call, email, and text asking me to reach out. I called and they basically said they wouldn't be investigating the malfunction since I didn't claim that was the issue (incorrect, which can be proven in my email chain a couple days after it happened and could be heard in the roadside assistance line that they usually record). They said there was nothing more they could do and I'd have to reach out to the original branch for any hope of getting the malfunction report, but it was unlikely. They are trying to make me pay the full bill which I shouldn't even be responsible for, and not only that, but they're refusing to properly investigate the issue. It's dangerous and neglectful in my case, but especially if they're making a habit out of not properly investigating malfunctioning vehicles. I almost died from it. Someone else could very well die from it. Any advice on what I can do here or any thoughts on how I can get out of it?

I live out of state but the car was rented and returned in Cali. The incident happened there as well. Location: California