Thanks to this post, I've manage to solve the slow download issue as I've just got the Falls Creator's update last week...didn't realize the slow download as the ping was fine for the first few days until there's a game update then I realize the speed is too low...
Updated to this FW version on the 8th Dec...so far so good...
no issue/lag when playing games like Overwatch...
just realized there's more supported games on WTFast now which is great! :D
https://wtfast.zendesk.com/hc/en-us/articles/210169943
I'm also facing this "Check connection..." message after flashing the latest firmware...i did a factory reset and it's still the same...
but since my wifi is still smooth, i didn't bother much about it...