Maybe the TTL was set too low and packet loss was being triggered by the TCP forced idle?
Or maybe it has something to do with this? Seems its using IPv6 tunnels and that might be causing the packet loss?
But your right..seems like EVERYONE is getting packet loss on the upload. I think anything under 10% is good? The rest is issues inherent in the test. Not 100% sure but thats my best guess from the short Google rabbit hole I just went down.