DisplayIncomingCall UI appears for a few moments -> then Disappears (IOS)

Bug report

• I've checked the example to reproduce the issue.

• Reproduced on:

• iOS

Description

This only happens sometimes, and I can't find how to make it consistent. But it is a critical bug for myself.
When call is incoming on IOS device, sometimes the DisplayIncomingCall UI displays, for < 1 second. Then disappears. The call is still incoming via my VOIP SDK but the incoming call UI screen disappears on IOS. I am not sure what makes this happen. The code is very simple.

Steps to Reproduce

• Call IOS Device
• Display Incoming Call UI
• UI Appears for a moment then disappears
  (Happens on randomly, but is critical as there is no way to connect the call when this happens)

Versions

- Callkeep: Latest
- React Native: 0.63.2
- iOS: 13.5.1
- Phone model: Iphone 6

Code

  const oneTimeId = () => {
    callId.current = callId.current || uuid();
    return callId.current;
  };

  const onCallListener: Listener = async (session, _userId, extension) => {
    ext.current = extension || initExtension;
    sess.current = session || initSession;

    const name =
      users.find(u => u.id === sess?.current?.initiatorID)?.name || '';
    const id = oneTimeId();
    RNCallKeep.displayIncomingCall(id, name, name, 'generic', true);
  };

Start with the linked example and trace the onCallListener path that invokes RNCallKeep.displayIncomingCall. Reproduce the intermittent iOS behavior using the reported React Native, iOS, and iPhone versions, then identify why the incoming-call UI disappears and verify that it remains available for the call to be answered.