I was a few chunks away from spawn in a world that was created in 1.14-pre2. I am unsure if the chunk had been loaded prior to updating to pre3. Upon trying to push and hit a pig, I was not able to do either of these things, but while trying to move through the pig, I was met with normal resistance. The pig didn't move even when I wasn't interacting with it. After re-entering the world, I noticed that other mobs were also acting in this manner. The map in my hand stopped updating, and my position on the map was also stuck in the position where I had first noticed the bug. Once this bug occurs, I am not able to save or crash the game normally, and I have to go into task manager and manually end the program to exit.
 
What I expected to happen was...:
the pig would move of its own accord, react to the player pushing it by moving, and react to the player punching it by turning red and fleeing.
 
What actually happened was...:
the pig did not move. it might as well have been an Armor Stand.
 
Steps to Reproduce:
1. load a Default world
2. create a map and enlarge it twice
3. walk away from spawn while holding the map in either hand and look for a mob
4. attempt to interact with the mob
5. attempt to save or crash the game