Great this way around worked for you as well.
Also, i have reported the issue to my local LG representative and waiting for a home visit to fix the problem. As soon as i got a solution from LG, i will post it here.
Hi,
I faced exactly the same issue after software upgrade to the latest version similar like you have. I found a quick way around to fix it. You need to disable "Quick start+" from the General settings tab. After doing that re-start your TV and bang Wi-fi speed will be back where it should be. It's just one time process and then streaming will work flawlessly.
Try it and hopefully it will work out for you as well.
/S