Internal call not vibration

[SPAdmin]

Good morning,
I am experiencing a problem with 3CX app on Android on Google Pixel 7a in vibration mode.
When receiving internal calls (both with screen on and screen off) the call makes a small vibration and stops.
External calls, on the other hand, vibrate continuously until the call is accepted.

I have already checked all the settings but cannot fix the problem.
Any ideas?

 

[RiesM]

Good morning,
yesterday i had a case where i got absolutely no calls showing up or vibrating, but the counter of missed calls rose up.
After reboot of that Pixel 7a i got a notification about a new feature from the system about „Benachrichtigungen reduzieren“ or "Notification cooldown".
After disabling that function, notification of incoming calls were restored.

 

[SPAdmin]

I have tried but the problem is still there.
I noticed a strange thing though.
If I call my number, the app doesn't vibrate. The call, by setting, diverts after 15 seconds to a group of which I am a member.
The moment it is diverted, the same call vibrates without a problem.

I cannot understand.