There used to be a lot of cats in my village,At that time, there was a bug that the game would slow down when the villagers are working. I think it was the problem of the cats because after killing them,  the game would return to normal until the cats appear again. But cats no longer appeared after upgrading the game.And iron golems never appeared in this village.Please look at the pictures I sent.

Picture 1:Here is my village and there are no cats or iron golems.

Picture 2:I used the instruction to kill all the villagers,It's strange that the cats appeared after that.

Picture 3:I created many villagers.

Picture 4:The next day, when the villagers start to work, an iron golem finally appeared