The flag system has always had glitches when it's not displayed for certain people. They are primarily there for my use anyway, and it's a "plus one" that I made them available to everyone. The wrong flag showing has been explained more times than I've had hot dinners, it's your internet provider which causes it not the forum software.
Not much I can do, however there's a new version of the forum software on the horizon which is a complete ground up rewrite of the code. I'm very tempted to switch to that once it's fully released which may mean we lose some features like flags anyway. A lot of new features, and they've revisited some of the existing ones and improved them.