After i have cured villager zombies, and made them become farmers with the composters, they didn't harvest. They just stand at the composter, looking and running around or chatting with each other.

I tested this issue in creative mode in flatland and 2 infinite worlds, in different biomes and with different fruit. Even with spawnig egg, until I got a farmer in the first place so no change of job was necessary. it is always the same. Farmers in naturally generated villages too.They don't want to harvest anything. When I harvest or destroy the wheat, potatoes whatsoever, they start to plant new ones, but only a few (1-3).

I even deleted minecraft and installed it new.

If they don't harvest, they don't get in the mood for multiplying...