Steps to re-create problem (Creative mode + superflat):

1. Select superflat generation
2. Click "Customize"
3. Click "Presets"
4. Use the following preset: minecraft:bedrock,2*minecraft:dirt,minecraft:grass_block;minecraft:jungle;jungle_pyramid
5. Create world
6. Use command: /locate jungle_pyramid
7. World freezes as if trapped within one game tick
8. Once command finally works (Can't find the temples), the game seems to update by one game tick (Mobs move a bit, spawn in, blocks update, redstone activates, etc., however fire and lava don't spread, which is odd)

Symptoms of Bug:

• All mobs behave as if the "No AI" tag is enabled until the command finishes and they move a bit again
• Mobs do not take damage right away, but it might be reflected a while later
• Mobs are stuck in place, mid-air
• spawn eggs take minutes (until the command finally finishes) to spawn a mob
• dropped items take minutes (until command finishes) to appear on the ground
• Cannot pick up items
• Can destroy blocks
• Player can infinitely fall into the Void (in creative)
• Day/Night Cycle and clouds still function as intended
• Can place blocks
• Cannot update block states right away
• Examples of the above: Pistons to not extend until command is finished, but then cannot be switched off right away

Then, I tried exiting my world normally, with the game being stuck saving. I Alt+Tabbed out, opened Task Manager, then ended the task (Minecraft). This exited the game and brought up the launcher, which said that the game had crashed (which is kind of true). Upon re-entering the world, everything updates and is normal again, until I use /locate jungle_pyramid again.