I am playing on a 1.7.x server (not sure the specific revision at the moment) that is basically vanilla with a bunch of mods. I don't run the server; I just play there.
I am working on an iron farm, following docm77's design (YouTube). I populated one of the villager chambers from two spawn eggs, and the remaining chambers were populated from the offspring of these two initial villagers.
This single platform has been working just fine, so I went to "pimp it up" (his words, not mine) and build the 2nd pod, directly above the first. I created a water elevator to move my offspring villagers, and populated the 2nd level cells.
The end result is that the villagers on the 2nd level are breeding, and I am getting golems, but the first pod has stopped producing anything.
On the first level, each chamber has 2 villagers, but I am not seeing any hearts above their heads, and no indication of any golems (the only golems I see are dropping from the sky).
Docm's video says that the 2nd level needs to be 70 blocks above the first - mine is 75. Would this be causing a problem? Would the elevator in place be causing a problem? Both pods are built the same, and I don't know enough about villager breeding and whatnot to understand what's the issue.