Broken progress with a service worker

[BrightSoul]

Hello everyone and thanks for such a useful project!
I'm using Evaporate version 2.1.4 in a Progressive Web Application (w/ service worker, if that's important) and the multipart upload is working wonderfully well. It's just the progress that's not reporting correctly and I can't understand why. First of all, here's my code.

Evaporate.create({
    aws_key: "REDACTED",
    bucket: "REDACTED",
    awsRegion: "REDACTED",
    awsSignatureVersion: "4",
    computeContentMd5: true,
    logging: false,
    customAuthMethod: function(signParams, signHeaders, stringToSign, dateString, canonicalRequest) { return myCustomAuth(canonicalRequest); },
    cryptoMd5Method: function (data) { return md5.base64(data); },
    cryptoHexEncodedHash256: function (data) { return sha256.hex(data); }
}).then(function(ev) {
    var params = {
        name: "REDACTED",
        file: fileReference,
        complete: function ()
        {
            //do nothing
        },
        progress: function (percent, stats) {
            console.log(percent, stats);
        }
    };

    ev.add(params);
});

As you can see, I'm logging to console both the percent value and the stats object. Here's what I see in the console. Percent stays at 0 for a while, and then suddenly goes up to 1. At times, it will stay at 0 for the whole upload duration. A very few times it's indeed working correctly but I wasn't yet able to determine in which conditions. This happens in Chrome, Firefox and Edge so it's not browser dependent.

Any advice on what might be causing this?
Thanks

[BrightSoul]

Nevermind, this might actually be related to this:
w3c/ServiceWorker#1141

I was listening to the fetch event in the service worker. As soon as I removed this, it started working correctly.

self.addEventListener('fetch', function(e) {
  var dataUrl = 'v1';
  if (e.request.url.indexOf(dataUrl) > -1) {
    e.respondWith(fetch(e.request));
  } else {
    e.respondWith(
      caches.match(e.request).then(function(response) {
        if (!response) {
          //console.log("Couldn't fetch from response", e.request.url);
        }
        return response || fetch(e.request);
      })
    );
  }
});

I'm closing the issue as it's not directly related to Evaporate but I'm leaving this comment here since it could be useful to someone else.