I have the S2 Classic - Bluetooth only. Screen lock is turned on and it works as expected requiring the pin every time I take the watch off. I leave it on at night for sleep tracking and put it on Do not Disturb to avoid notifications. Every morning, the screen is locked and I have to enter pin. If I use Do not Disturb during the day for shorter periods, the screen does not lock. Not a big deal but wondering if others experience the same.