I'm finding DND very buggy these days. I have two automatic rules set up, one for weekdays, one for weekends, to keep the phone silent overnight. Mostly they work fine, but maybe once a week (not always on the same day!) the DND just doesn't activate. Usually I only discover this when I go to bed, plug in my phone to charge, and it plays that massively annoying 'now charging' noise at full volume, waking up my wife...
If I go into the DND rule, and toggle the 'rule enabled' switch off then on again (while the DND is supposed to be active), the rule still doesn't reactivate, and DND stays turned off. But if I toggle its "Alarm can override" switch, then the rule reactivates, and DND turns on. Which is a weird little bug in itself.
But *then*, having done all this, I usually find DND doesn't turn itself off again at the time specified by the rule. Instead, I get halfway through the morning before realising it's still waiting for me to manually turn it off.