I wanted to reset the trades for the librarian, so i broke the lectern and he didn't lose his job, then i noticed it also happens for the rest of villagers.
Comments 3
As misterblue28 said, the problem may be that you have traded with them already. In the newest versions, villagers won't lose their profession and "lock" their trades if you trade with them at least once.
Have you traded with the villagers already?