„Repeated calls“-function not working

What leads you to this conclusion? I don’t recall ever seeing anything suggesting this behavior.

From what I read in the settings ("A second call from the same person within three minutes will not be silenced.") means that if a favorite calls two times within three minutes, the phone will ring, independent a) being in "Do not disturbed" and b) the hardware-mute-switch being switched on. This would be the ideal behavior at night: Phone is always silent (only vibrates) during the day, with the same being true at night, except for favorites when, if they call twice (and it appears to be urgent), the phone will also ring at night.

Is there a way to achieve this? Or am I missing something here?

You should update to the current iOS version: 14.6.

Sry, was a typo above, I was already on 14.5 and went to 14.6 this morning.

Thanks.

And coming back to the original question: How do I achieve that my favorites can reach me (e.g. at night) by calling twice within three minutes and cursing the phone to ring (not just vibrate) even though I’m in DND and hardware-mute-switch being switched on?

Right now my phone does not ring at all in the scenario described above, let alone differentiate between favorites or not.