Villagers that have been traded with whose job site blocks are broken do not get priority over other villagers when that job site is replaced. Other unemployed villagers are just as likely to take that job site block (and become that profession), leaving the original villager without a job site but still stuck in their previous profession.

This is especially annoying when there are many unemployed villagers.

What I expected was...

The villager whose job is locked in gets the newly-placed job site.

What actually happened was...

Instead, an unemployed villager took the job site block and became that profession.

Steps to reproduce...

1. Place job site block to give a villager a profession
2. Trade with villager to lock in the profession
3. Break job site block
4. Spawn a few unemployed villagers
5. Re-place job site block. Most of the time, an unemployed villager will take that profession, leaving the villager with the locked profession without a job site

Example:

JobSiteStolen.mp4