This is in a Realms game on a Samsung Galaxy S6 running 0.15.0 Realms Alpha build 4.

What happens: aggressive mobs that should burn in sunlight (i.e. skeletons and most zombies, not wearing helmets) may not burn in sunlight.

This seems to happen most often when the monster has spawned and is not yet burning, I quit and reload the realm and the monster enters sunlight but does not burn. There may be other factors at play.