Summary:
Game freezes if Dragon's breath doesn't reach blocks. This can be reproduced in many ways.

• Die during a dragon attack.
• Teleport a long distance while attacking.
• Remove blocks before Dragon's breath.

You will not be able to exit the world due to the infinite world saving. Reloading minecraft returns the world to normal. This can sometimes result in MCPE-159285 (world corruption).

Steps to reproduce (1):

1. Turn on Immediate Respawn.
2. Go to End.
3. Wait for the Ender dragon to land on the portal.
4. Use /kill @s while starting a breath attack (you can wait for the Ender dragon to roar).

Steps to reproduce (2):

1. Go to End.
2. Remove all blocks around the end portal.
3. Wait for the Ender dragon to land on the portal.
4. Switch to survival to have the Dragon start a Dragon breath attack.

Observed results:
The world is completely frozen. You can visually walk, break blocks (but no particles). Exiting the world leads to infinite saving.

Expected results:
The world will not freeze.

Video:
Minecraft 2022-08-19 16-59-32.mp4