I had one that would work, but only if you rotated the knob very slowly. So if you turned the car on and the music was deafening, you had to oh-so-slowly turn down the volume with one hand, while trying to staunch the bleeding from your ears with the other hand.

The rotary encoders typically require quite fast sampling (~1000Hz) to be reliable when turning fast (it can be also done in hardware though). They are probably running a whole RTOS on that poor microcontroller that controls radio, so can’t afford so much processing power ;)

While an awful situation, I couldn’t help but laugh very much at how ridiculous it is. Thanks for this comment.

That's hilariously bad design

In our Subaru, the radio comes on, but you can't turn it off for at least 10 seconds, and then it might come back on, depending on exactly how many times, and when, you tried to turn it off earlier.

I have a Toyota Camry and I haven't timed it but I think it's more like 10 seconds. Before that neither the volume knob nor the on-off button work.