Zer0Cool It’s not so much “the computer” that’s the problem; it’s more the question of the effort put into the software, and specifically the redundant backup systems that are required in safety-critical systems such as these. If the developers took shortcuts, especially once the bean-counters start breathing down their necks, problems may appear.
One example was insufficient isolation between fixtures and vehicle control in some models of Toyota vehicles, that made them far easier to steal than they should ever have been. There was also the Hyundai infotainment system that seemed to use open-source sample code for its security, including the hard-coded encryption keys, allowing one customer to entirely commandeer the system, replacing its software.