The function of the villagers to spawn iron golems is abnormal

The map is an iron golem farm. When the villagers are scared by zombie, they totally spawn 4 iron golems at the same time. It does work in 1.19.2 and up. However, the villagers only spawn 2 or less iron golem when they are scared in 1.21.4.

 

(Sorry for setting the video link in private. Now it is public to everyone)