I have attached a python program that demonstrates this bug. Basically, at one point in the program, both subscribers are receiving messages just fine (the sleep allows the socket time to setup, on my system). After closing subscriber1 socket, we publish another message and subscriber2 cannot receive it, it just hangs. This is not a late subscriber problem because we do receive a message earlier in the program.
Also, I ran this test script on 2.1.11 and it works fine.