^{Update by Auldrick}

Hostile mobs spawn a light levels 8 or higher on both solid and transparent/non-solid blocks.

• Updated *

Original description:

I think there is a problem with hostile mobs, and may require a cumulative fix.

-Monsters often won't despawn in the overworld.

-Spawning cages stop working after a few days of functioning normally.

-They are spawning in high light-levels

-They are spawning on half blocks/transparent blocks

-The nether fortress becomes empty after killing the mobs inside.

All of these combined lead me to believe there is a cumulative issue with mobs spawning. My theory was that the game fails to recognize the environment correctly (when it scans for mobs), then spawning becomes erratic.

The worst part is that the cages in my mob farms have completely ceased up.

All of this is occurring on a world that was synced and added to a Realm.

Please check into this! Thank you.