OL would be the complete opposite of a dead short, also, measuring resistance in-circuit is pretty pointless unless you have a known-good to compare to, given you have no idea about what might be in parallel with the measured component.

The parts getting hot would be my first port of call, seconded by any passives that are directly attached to said parts.

Get the datasheets for the hot parts and check that their power carrying pins (could be supply, or output if they are driving the head motors for example) aren’t shorted. If they are then remove the parts and re-check for shorts.

I should make sure my ST-157A still runs.

You probably need to manually manipulate the stepper back and forth a bit. It is probably just stuck due to disuse. Chips might be getting hot trying to feed enough current into the stepper motor to get it to shift. If you are brave, take the circuit board off and see if you can manually manipulate the stepper.

Good capacitors should always have extremely high resistance once they are charged, so the multimeter readings don't mean much.

The spindle motor didn’t run either, it needed a few gentle hits on the head.
I’m not sure how to convince the stepper motor though, but I’ll take the board off and see if I can get it going

Stepper motor is still not moving. It has a 6 pin connector of which 2 pins show 4.5V.
I can rotate the spindle though so probably some faulty component on the board, I don’t know. Besides, to remove anything on that small board I’d need a microscope, hot-air station and skills😬.
Too bad the drive doesn’t work, but hey it’s 23 years old.
Going to scrap it.

Apply some lubricant to the axel. That may help reduce the friction of the stepper.
I always use PTFE spray, others use silicon oil or oil for sewing machines.
Maybe it helps 😀