What I expected to happen was...:
Villagers will always try to go to their job site blocks even if you take them and block their path to their job site blocks and after you free the pass, they will go there.

What actually happened was...:
When pass one day in the game and the villagers didn't "work" during the day because you blocked their way to their blocks, the next day they don't go to their job site block. This occurs to villagers without work, too. They don't take any work. They don't detect the job site block.

When it occurs, another villager without experience take the job, ignoring the experienced villager. This in the snapshot 20w22a was added and here you experiment this issue.

Steps to Reproduce:
1. Take a working villager and he's at his job site
2. Block his path and transform him in a zombie villager.
3. Cure him and check it that the villager don't detect the job site block
4. You can put a villager without experience and you're gonna see that he's gonna to take the job, ignoring the experienced villager.

Everything happens when the villagers work and not when they are in gossip mode at nightfall.