Your first test result shows 4.81 / 2.17 Mbps. Your second test result shows 12.39 / 1.04 Mbps. As I said in my first post: "This is assuming your upload is reasonably stable.".
Obviously, your connection is not stable when doing these tests. Are you using wlan instead of wired when doing these tests? Do you have other people using the connection when doing these tests? If not, it's worth trying (as idxman01 suggested) to re-do the test without the er-x.