I am in the same boat as that guy. My Xbox One is downstairs, in the same room as my Virgin Media SuperHub 2. I am using the 2.4GHz wireless connection to play online on my Xbox. The only two games I play are: FIFA 16 and GTA V. When I am playing FIFA, I have no problems whatsoever. But whenever I join ANY online session of GTA, after a few minutes I am getting kicked off of Xbox Live for a few seconds. Not just off GTA Online, but kicked off Xbox Live completely. And then as soon as I go to the dashboard, I am reconnected and everything appears fine.
Believe me when I say I have tried pretty much everything to solve this. I have contacted Rockstar, posted on their forums, posted on the Xbox forums - nobody has a solution other than "try these troubleshooting tips." I have restarted my SuperHub multiple times, cleared my Xbox cache multiple times, I have tried portforwarding all the ports recommended by Rockstar for GTA Online, I have turned off/on UPnP, I have even tried uninstalling the game & deleting my save data and then reinstalling it and resyncing my data from Xbox Live. Still, nothing has worked.
I have an Open NAT Type and no, I haven't ever had any problems connecting to other people/online sessions on any other games I've played on my XB1. Someone please help me fix this, as it's really quite awful only being able to play 50% of my Xbox games.
Welcome to our forum, sorry you are having problems with GTA, I can feel your frustration.
I have checked your line and hub and as expected it all looks good, would it be possible to try an Ethernet lead just to see if it worked okay rather than wireless and then if not perhaps for diagnostic purposes modem only mode
Also I appreciate that you have all the correct ports forwarded and you mention an open NAT however would DMZ mode in the hub help I wonder.
Please let us know how it goes if you try anything.