Failed to Connect to Instance

I've searched and searched for well over a week, but I can't find an answer.

About a week ago, I started getting failed to connect to Instance when changing zones. It disconnects me, and I just have to log in again. It doesn't happen every time, but pretty consistent.

Has anyone had this problem and solved it? I was going to run a game files validation check, but I'm using the standalone client and not steam.