Oppo
Enable Vibration in Silent Mode auf Oppo
On most Android phones, silent, vibrate, and sound are three separate modes. ColorOS handles this differently: silent mode is a single state, and vibration only works inside it if you turn on a dedicated toggle.
Without that toggle enabled, switching your Oppo to silent stops every buzz along with the ringtone. Calls, messages, and app alerts all go through without any physical feedback, which is easy to miss in a bag or pocket.
To fix this, open Settings ➔ Sound & vibration, then find the option for vibration during silent mode and switch it on. Once enabled, your phone stays silent for sound but still vibrates for incoming calls and notifications.
You can turn the same toggle off again if you want true silent operation with no vibration at all, for example during meetings or at night.
This setting only affects behavior while silent mode is active. Normal ring mode is not touched, so vibration for calls and notifications there depends on your regular sound settings, not on this toggle.