Games run very slowly when leashing stationary Happy Ghast to fance

When riding Happy Ghast and park it with trapdoor above its head, it stop moving. Then, I leash it to a fence with block preventing the Happy Ghast following the lead. Suddenly, the game run very slowly. But fps does not reduce.

The games runs fine after

• The Happy Ghast is killed. or

• I cut the lead with shear. or

• The Happy Ghast is moved to position that it can move itself. or

• Player go away and Happy Ghast is unloaded. The games runs slow again if player go back to the Happy Ghast.

To reproduce, follow the video I attached or here is the step

1. Make a 4 blocks high pole out of full blocks.

2. Place trapdoor on the side of topmost block.

3. Ride Happy Ghast into the trapdoor and close. This will make the Happy Ghast stationary.

4. Place a fence 7 blocks away from the pole then leash the Happy Ghast to the fence.

Even after removing trapdoor or some blocks from the pole so that the Happy Ghast stay still, the games now runs like turtle.

Player can still move like normal but interaction with the world is slow. The game still retain fps.