you have to push right on the d pad to look through them once equipped and aiming down sights then it will stay and you press and hold right on the d pad to go back to iron sights they are working fine.

I can't speak for South5 but for myself it is whenever the game app is closed and restarted so crashes are included but not the cause.
every day when I sign in I have to turn inverted controls back on. hope this helps thanks !

this is almost word for word what I came here to say I SECOND THIS SO HARD!!!!!