The Firefly particles produced by the Firefly bush continue to be active for some time even after the game has been paused.

Steps to reproduce:

1. Launch Minecraft Preview (1.21.70.20)
2. Create a new world in creative mode
3. Place down a few Firefly Bushes
4. Set the time to night (You can use this command: /time set night)
5. Pause the game

Expected Result:

The Firefly particles freeze in place, and to not disappear.

Observed result:

The Firefly particles continue to animate for some time and then eventually disappear.

Notes: 

This is related to the issue mentioned at MCPE-188461.