In the most recent 2 snapshots in the same seed, I have seen a novice villager attach to a job block and kick out the villager that I have traded with.

The village is about 170 blocks away from my base and twice now I have entered the village to find that a novice has taken the job block of someone that has already been traded with.  The block was not broken.  I went to the village and there are now 2 villagers with the same job where there should be only 1.  The one that has been traded with still has his job and just wanders around town while the novice takes the job block.  The first was a cartographer, I fixed that issue on an older snapshot (broke the block, let him lose the job and wander away, put it back for the master to take).  Today with the newest snapshot, it happened again with a cleric.  I backed up a copy as soon as I found it in case that is needed.

First was cartographer, this time it is the cleric.