Hey Marc-Andre,
I believe we've managed to determine a little better what's going on. The gapi client library uses static/proxy.html for cross domain requests. As for the errors you're seeing, it would seem the JS client is failing to make calls due to network errors. So, the proxy requests are working correctly, but the errors are likely due to network problems for the clients.
I hope this helps to track things down further. Let me know if you have any more questions!
Cheers,
Nick
Cloud Platform Community Support
On Wednesday, July 20, 2016 at 11:49:07 AM UTC-4, Marc-Andre Bruneau wrote: