Resistor chip, transponder keys, and the latest scheme using a standard key with Hall Effect devices that output a signal if the correct key is inserted and the tumblers are properly aligned. All can give problems, with the Hall Effect, key can still work, but the teeth are worn off. Getting a copy off the key is not a solution for erratic operation.
Certainly doing a far better job of preventing the rightful owner of the vehicle from starting and running their vehicles than prevent thief. If they really want your car, just need a flat bed truck, don't even need a key.
Besides that key, have literally millions of electrical connections, most are buried inside integrated circuits. Unlike a single sided PCB, not only have runs in the two dimension plane, but also in the vertical plane as well. But with erratic problems, most likely is an erratic switch contact that fails to give a proper power on reset. Just a tiny capacitor does that pulling the reset pin for the microcontroller reset pin to a low. If not properly reset, program counter is not reset to zero and starts off down stream screwing every thing up. Firmware can be written to be self correcting, but all depends on how sharp that guy in India is that writes this stuff.
Dirty ignition switch contacts can cause this problem. With an engine killing erratically, your guess is as good as mine. How about connecting a fuel pressure gauge, hot wiring the fuel pump, and draining the gas into a clear container. You may find water in the fuel. Also have a million connections for the fuel injectors and ignition. Don't even want to think where the problem could lie in these situations, in particular an erratic problems.
Usually in the connectors, not looking for anything major, could be just a mild amount of corrosion on one pin.
Oh for the days with an engine driven fuel pump, and a set of points for the ignition, so much simpler back then. What use to take five minutes, can consume an entire weekend, or even more.