Recently Tantrum and I have been having issues with our custom chat channels upon login. The certain chat channels disappear even though a /who or /whois command will show you in the channel, other occupants of the channel still see you as present in the channel.
You cannot participate in the channel, but the chat from that chatroom defaults to whatever window you are currently in. This also happens in in-game lobbies and in the game itself.
To recreate this bug: We've found that any player that hops between computers on the same account gets this issue, Tantrum and I play at lan centers. We've also spoken with others and found that they also play on multiple computers. Clan channels don't seem to be affected by it at all.
Ways to counteract it: Relogging is an inefficient way, but sometimes it works correctly. Getting the admin of the channel to kick you and rejoining is also another solution.
As you can see, the custom channel EqPriest shows up in my /whois, but does not appear on the left list channels.