Mobs stop spawning with "Multipack" DLC.

Greetings,

Yesterday I just opened a realm with Multipack World but after some hours the hostile mobs suddenly started to disappear. Also, the night did not end even if we slept. I ended up resetting the realm but I'm afraid it will happen again since before starting to play it it's not the first time to happen where mobs are nowhere. Is there a bug with this Multipack realm?