Video Call - 1 device is loud but 1 device is very quiet

Explanation

When making a video call between 2 phones via WebRTC, I can hear very clearly through the speaker on the first phone (IOS 13, iphone 6) but the other phone is nearly always quiet (barely hear from speaker) (IOS 13, iphone SE). Sometimes it works but usually I cannot hear much.

Code

This is my implementation:

    Wazo.Phone.on(Wazo.Phone.ON_CALL_ACCEPTED, async (sess: any) => {
      if (isCall || ready) return;
      session.current = sess;
      const sipSession = Wazo.Phone.getCurrentSipSession();

      if (session.current?.cameraEnabled) {
        const { peerConnection } = sipSession.sessionDescriptionHandler;
        const lStreams = peerConnection.getLocalStreams();
        const rStreams = peerConnection.getRemoteStreams();

        const anyTrack = (stream: any) => !!stream.getVideoTracks().length;
        local.current = lStreams.find(anyTrack);
        remote.current = rStreams.find(anyTrack);

        if (!isIOS) {
          RNCallKeep.backToForeground();
        }
        await inCallManager.start({ media: 'video' });
        await inCallManager.setSpeakerphoneOn(true);
      } else if (session.current) {
        await inCallManager.start({ media: 'audio' });
        await inCallManager.setSpeakerphoneOn(false);
      }

      await sipSession.sendReinvite();
      dispatch({ ready: true });
    });

Env

    "react-native-webrtc": "^1.75.3",
    "react-native-incall-manager": "^3.2.7",
    "react-native": "^0.62.2",
    "react": "^16.13.1",

Start with the reported ON_CALL_ACCEPTED callback and the react-native-incall-manager calls in the supplied implementation. Reproduce the WebRTC call between an iPhone 6 and iPhone SE on iOS 13, then inspect speaker routing around start, setSpeakerphoneOn, and sendReinvite. Done means audio volume is reliably comparable on both devices, with a focused reproduction or test if the project supports one.