How much precision are we talking?
I'm only guessing this isn't something where you need to be back in the same position within seconds of angular rotation...

In all honesty, given it's only a Nema 14 motor, the voltage isn't going to be that great, and the amount of generated electrical noise isn't going to be that great either.

If rotational drift is a concern, then you could implement a position reset whenever the opto gets triggered.