Do not disturb mode doesn't work after upgrading to Android 12

I've got a OnePlus Nord CE 5G. "**Do not disturb**" mode was working fine with **Android 11**. Since the upgrade to **Android 12**, it stopped working properly. It shows as activated but I keep getting **some** notifications and sounds (not all of them, but no clue which ones they do and which ones they don't). The settings are correctly configured to **not** get any notification from any application, and still, I keep getting some even with the screen lock. Any idea of what to do or how to go back to Android 11?