How to turn off WhatsApp Call vibration during Do Not Disturb Mode

Hello.

This night my iPhone 8 was in "Do Not Disturb" Mode and in "Sleep Mode" [1]. Suddenly my iPhone vibrated and was showing the "Sleep Mode" Lockscreen [2]. I unlocked my iPhone and it still didn't show anything. I opened WhatsApp and I saw a WhatsApp Call.

Why didn't work the "Do Not Disturb" Mode and the "Sleep Mode"?

Usually all WhatsApps text notifications are turned off and I don't get disturbed. Here are my "Do not Disturb" Mode settings [3], here are my WhatsApp Settings [4] and [5].

Is there a way to turn off WhatsApp Calls during the "Do Not Disturb" Mode?

Was is it just a bug last night?

[1]

[2]

[3]

[4]

[5]