Mobs from caves spawn on surface during the day

Monsters and bats spawn during the day on the suface of the world. Since there monsters, slimes spawning in non-swamp biomes, and bats, it seems like these mobs are getting teleported from underground cave systems.

How to recreate:

1. Create a default world
2. Find a large area of open land

You will see Hostile mobs and bats spawning on the surface during the day.