Entities and block entities despawn after a while

Every entity despawns after a while or when walking 64 blocks away from an entity. Item frams, passive and hostile mobs, signs, and maps all despawn.

This problem only happens in infinite worlds.

I noticed that in creative, if you fly up in the air and you come back, all entities are gone.

Problem since: 0.12.1

Devices tested:

iPod Touch 6th Gen
iPhone 5S
iPhone 4
LG Optimus L90 D415