The End Crystal animation can stop playing and display as a block
Steps to reproduce:
- Place down a repeating command block with the command: summon ender_crystal ~ ~1 ~
- Activate the command block and wait for a few seconds
- Go up to the command block, look at it's edge:

- Sneak
Observed result:
The animation stops playing and the end crystals display as if they are a block.
Expected result:
The animation continues playing like usual.