not sure whats going on but few things you can try.
try to switch media player. try a vpn. if using vpn then try without vpn. try to use on third party app on your box and see if it makes any difference. it might be your isp. try a diffrent server because it might by your server. so more testing and info required to understand whats going on.
Great. See if they have an option to use a username/password instead of a Mac. If yes, then you don't have to reset evertime when you switch devices or apps.
try clear cache and see if that helps. also, switch media player might help too.
also you should be at 9.0.935 if im not wrong. I dont have that box but I believe it should be at .935
try to click update from setting from live tv and see if that helps.
after reading about this device this device nothing but helps with noise cancelation sound related. this clearly tells that there problem in your network. you said all passed on your test gear, but like emporium said pass mean nothing. and you know that you still got noise and noise filtering helped you but you are still having intermittent issue. it did not resolve 100%. what does this tells you? we dont have noise issue and thats why we dont see this problem.