With the latest Minecraft update, monsters are no longer spawning on my world in multiplayer sessions.  The game is set to Hard/Survival difficulty, with everything else on default.  I started this world prior to the latest update, and everything was behaving fine until now.

Both myself and my girlfriend play on this world together, and we noticed after the latest update that no matter what we do, or where we go, there are no longer any monsters in our world at all, including the phantoms after 3 sleepless nights, so long as both of us are playing at once.  If only one of us are playing, monsters start to spawn again.

To encourage monster spawning, we have tried sleeping, playing through various nights, travelling long distances, however the world is devoid of all monsters.  I verified my settings are not on Peaceful and that cheats are not enabled.