Iron golems not going trough nether portals when spawning

When an Iron Golem spawns on a platform with nether portals they do not go trough as they did in 20w27a 

What happens is they just sit their walking trough them but not ever getting telported even when they sit still. 

To reproduce

1. Create a bunch of nether portals like the files 
2. Wait in a spot or spawn an iron golem and they will not go trough most of the time or make a villager farm were it can spawn iron golems shown in the screen shot make sure a hostile mob is near so they actually spawn it