XHR only works once with Firefox on production site

[TheoChevalier]

Played a bit with download buttons, noticed that stats are recorded only for the first click in Firefox. e.g., if you download two builds from Firefox, we will only record the first one. This does not reproduce locally, and does not affect Chrome. I think we had the problem since the beginning, but it only occurs with HTTPS.

In Firefox Network devtools, the first XHR is marked as secure, the second one is marked as not secure. Even though in both cases query URL starts with https://

Not sure if the problem comes from the jQuery lib we’re using, our code, or Firefox.
Same behavior with Firefox Release or Nightly.