When iron golems are spawned with this iron farm: https://www.youtube.com/watch?v=tlhwHi7i0pM&t=135s&ab_channel=NaMiature

the iron golems that are spawned in platforms will not go through the nether portals into the overworld most of the time. This causes the farm to be reduced in efficiency about 70 percent. (please see attached image)

the iron golems do not go through the portal for around 10 minutes. before a certain amount of time, pushing the iron golems into new portals will not work.