The bug

I was playing around with some execute commands on a slimeball to clear out a 30x30x30 area of sand. While i mistyped the fill command and threw the slimeball on a 1x1 pillar that reached the building height limit (i knew it wouldn't work), entities already loaded became "frozen" and shaking in place, and new entities would not render, making them invisible.

Steps to reproduce

1. Go to a world/Create a world _{(recommended superflat)}
2. Make 2 pillars that reach the building height limit, one of any block, the other one of sand
3. Place down 2 repeating command blocks /give @p repeating_command_block
   • In the 1st command block, copy-paste the following and set to always active:

     execute @e[tag=slimeball] ~ ~ ~ fill ~15 ~15 ~15 ~-15 ~-15 ~-15  air 0 replace sand
     

   • In the 2nd command block, copy-paste the following and set to always active:

     scoreboard players tag @e[type=Item] add slimeball {Item:{id:"minecraft:slime_ball",Count:1b,Damage:0s}}
     

4. Get yourself a slimeball and go on top of the pillar
5. Place some sand on air to check if entities render properly.
6. Throw the slimeball on the pillar and take it.
7. Repeat step 5.
   See that the slimeball and the falling_block entity be invisible, and if there would be any other loaded entities, they would "freeze".
   To get rid of the effect, reload all chunks by pressing F3+A

EDIT:It might not work sometimes, now i can't reproduce when i went in and ouf of fullscreen mode.. Weird.