Now think about that ping.
Why should servers service a ping quickly? It's a waste of their time so no real reason to answer it.
But that is not where I want to go here. As you are successfully uploading a video to a big site, you don't have much to get support yet for. It works, just that it pauses at times.
Also, on WiFi it's half duplex, but you know that.
Finally, it appears you have only this issue with this one site. Why do you think there is something wrong with your computer or network?