All mobs hostile towards iron golems will go to village centers and will attack the air. - It seems like the mobs AI think that there is an iron golem there, when there isn't. - Projectiles will also bounce off the 'invisible' golem too.
Linked issues
is duplicated by
Comments

Also can confirm. They attack Village Squares thinking there's an iron golem. When you reload the world, the iron golem spawns.
So the iron golem exists but it's invisible and invulnerable???

Confirmed on 1.14-Pre2

Also affects Villagers at the start of another wave unexpectedly; they become "ghost villagers" and do not disappear until reloading the world during the raid... (Located a Ravager & some Pillagers all attacking an invisible & invulnerable Mason in the Village... Projectiles did bounce!)
Can confirm. This was observed in xisumavoid's snapshot video.