Webrtc: Cannot see remote stream in Firefox but works in Chrome

Question

I recently restructured my working webRtc code, replacing some deprecated APIs and some other restructuring. It continues to work in Chrome but not in Firefox anymore. The basic structure of the code is shown below:

navigator.mediaDevices.getUserMedia ({ audio: true, video: true })
  .then(function(localMediaStream) {

     //Show local media
     document.getElementById("myVideoMedia").srcObject = localMediaStream;

     //create peerConnection
     peerConnection = new RTCPeerConnection({
       "iceServers": [{"url": "stun:stun.l.google.com:19302"}]
     });

     peerConnection.ontrack = function(event) {
       remoteStream = event.streams[0];
       document.getElementById("remoteVideoElement").srcObject = remoteStream;
     };

      peerConnection.onicecandidate = function (event) {
         if (event.candidate != null) {
           //Send ice candidate to peer connection..
         }  
      };

      peerConnection.addStream(localMediaStream);

      //Show remote media
      document.getElementById("remoteVideoElement").srcObject = remoteStream;

     //If caller, send video invite to callee to do the above in its browser
     //if callee, having received video invite, send message to caller to request sdpOffer


});


//When (on caller's side) request to send sdpOffer is received
 var sdpOffer = new RTCSessionDescription (offer);
 peerConnection.setLocalDescription (sdpOffer)
    .then (function() {
       //send sdpOffer
    });


//When (on callee's side) sdpOffer is received 
peerConnection.setRemoteDescription(remoteSdpOffer)
  .then(function() { 
     peerConnection.createAnswer()
       .then(function(sdpAnswer) {
        var sdpAnswer = new RTCSessionDescription(sdpAnswer);
        //send sdpAnswer 
        peerConnection.setLocalDescription(sdpAnswer)
          .then(function(){
             ...
        })

//When ICE candidate is received
peerConnection.addIceCandidate(new RTCIceCandidate(iceCandidate))
  .then(function() { //console.log("Remote Ice candidate added");
})
.catch(function(err) {...});

The remote video is not seen in Firefox, irrespective of whether the Firefox browser is a caller or a callee. I suspect that it has to do with some sequencing of event handlers but cannot locate which one...