Villager profession

When I try to search for a good trading with villagers, I found that during night the villagers keep changing from employed to unemployed and vice versa when I break the workstation.

This error Includes the change from a profession to other.

 

Edit: In stable version you can continue searching for a good trade until the sun is in certain position in the sky and the job gets locked until next day. This don't happened in snapshot.