Bottom line: don't trust it, use something else until it's fixed. Just adding my voice to the chorus advising that this app is terribly broken after the Android 12 update, especially for countdown timers, which run but don't advise you in any way that the time is up (not even if you're actively using your phone...you'll simply go back to the app after you remember and it will show how long it's been since it was supposed to go off).