reset

Don't bet on that - a correct reset pulse will guarantee that the chip is in a known state. A too short reset pulse will leave the processor in an unknown state - and it can matter what state it was in before the too short reset.

So some programs can survive better if the reset pin isn't correctly handled. With a bad reset signal, the CPU core might be reset while some interrupt source might not have enough time to properly reset - and the end result is that you might get an interrupt that jumps into undefined memory.

So - a correct reset but bad software can (but maybe not always) give random failures.
And correct software with a bad reset can (but maybe not always) give random failures.

In short - you need to make sure that both your code and your reset signal is correct.

Don't bet on that - a correct reset pulse will guarantee that the chip is in a known state. A too short reset pulse will leave the processor in an unknown state - and it can matter what state it was in before the too short reset.

So some programs can survive better if the reset pin isn't correctly handled. With a bad reset signal, the CPU core might be reset while some interrupt source might not have enough time to properly reset - and the end result is that you might get an interrupt that jumps into undefined memory.

So - a correct reset but bad software can (but maybe not always) give random failures.
And correct software with a bad reset can (but maybe not always) give random failures.

In short - you need to make sure that both your code and your reset signal is correct.