Crash log:

https://pastebin.com/Rz5MCPcd

Explanation

I came across this after one trying to design a machine which would place and pickup chunk loaders so a machine could be moved a large distance (using dispensers and waterwheels with clutches so they don't break each other).
If a chunk loader becomes attached to a moving create machine the game will crash with
"Error: java.lang.IllegalStateException: Pose stack not empty"
The world often can not be loaded after this causing the same error again.

Simplest way to recreate this issue

1. A mechanical sticky piston with extension
2. A Chicken Chunks chunk loader
3. Attempt to move the chunk loader

For anyone else who has this issue

You can delete the chunkloader causing the problem following this guide

1. The file to edit is in the region folder, Select all of the .mca files and open
2. Find the chunk the machine was in
3. Find the entity
4. Find the block, delete the entry folder for it
   

This issue has been marked as stale because it has been inactive for 3 weeks. It will be closed if it remains inactive for another 3 weeks.

This issue has been closed since it has been inactive for 3 weeks since it was marked as stale.