abhibhuju , via OnePlus 9 Pro Stellar Black , Jan 26, 2022 : Screen doesn't wake up during the alarm.. Earlier it used to wake up..
kanishkkakkar , Jan 26, 2022 : The clock app was probably in your hidden apps when you ran the update. Remove it from the hidden apps to fix the issue.
W1617299376507 , Jan 26, 2022 : If your physical alert slider is on silent, the screen doesn't wake up.
Shailender Sharma , Jan 26, 2022 : If the clearing cache of the Clock app in the Settings and restarting the device for once doesn't resolve the issue. You may try, the Google Clock.
abhibhuju , via OnePlus 9 Pro Stellar Black , Jan 26, 2022 : The alert slider was not in the silent mode..
pjsaloneplus9pro , via OnePlus 9 Pro , Feb 7, 2022 : I have the same problem, even did a hard reset and nothing... Did you manage to work around the problem?