Iron golems only spawn on villager rooftops

In taiga village the Iron Golems and cats are trapped on the rooftops. The golems cannot come down and protect the villagers.

Steps to Reproduce:
Find a village in the taiga with enough trees. Observe how the golems spawn.

Observed Results:
The golems spawn and get stuck on the rooftops.

Expected Results:
The golems spawn on the ground to protect the villagers.