Major bug needs Attention! Mobs/Entities Disappearing!

The bug:

Whenever a server restarts or crashes or rejoining a single player world mobs/entities can disappear randomly even when in loaded or unloaded chunks.

Reproduce on a server:

• On a server if you have a bunch of tamed horses in a fenced up area somewhere in the world, if having other mobs as well that are tamed like wolves & cats, having boats & minecarts around the world, plus item frames in areas.
• Stopping your server and starting it back up a few times or even once can cause all those mobs/entities to randomly disappear.
• If the server were to crash the same bug can still occur.