It is because the minecraft client only allows a max string length of 16 characters.
I also had it when i was working on my map.
I had the Lobby having the prefix of §4§l[Lobby]§r
And everything worked fine.
But on the spectator team. §4§l[Spectator]§r that didn't
But if i removed only 1 character from it, it would.
And that was because the string was 17 characters long. which it doesn't support.
This will only show up when it is on a server tho.
They never connected to eachother and isn't a bug i think.
It are just 2 diffrent blocks that need a full block to connect.
Not a bug, it is a feature.
For people who are killing mobs in creative and if they miss they doesn't wreck the building or w/e
This is still a issue in 1.6.2 at me.
Singleplayer and Multiplayer