The villagers need to be able to see the zombie some of the time, so they think they need a golem, but not all the time, they need to use their workstations and beds.
It doesn't matter if they get back up as soon as they lie down as long as they lie down.
Are they laying down at night and do they use the workstations?
If you hang around up there you should be able to hear them use the workstations.
Docm's farm. I have this too. Occasionally stops working, not sure why. When it does I use a few solid blocks next to the zombie to block line of sight at night. This kicks its back off again.
my reasoning is that villagers only work at certain times of day (them working at their job-site blocks causes iron golems to spawn) and if you keep it running they should keep spawning this happened too me...
does this type of iron farm need to be in a specific area of a chunk?
cuz i accidentally built mine in between two chunks and its not working