Not getting calls randomly

Notifications for mentions are going okay, but when someone calls me it goes randomly ether to my phone or PC or both or sometime even none. Now i got a call from someone, and it started ringing on my phone while i was on my pc. Discord was running and the tab was open but minimized, but it did not start ringing until i opened the persons dm itself. Sometimes it starts ringing / showing notification only on second or third time a person tries calling me...