Villagers lose sight of occupation blocks

A bed and a work block were installed and villager A was employed.
Traded to prevent Villager A from changing jobs.
After confirming it, I confined it in the 1 * 2 * 2 block space along with the work block.
But villagers A lost sight of the work block.
Instead, a nearby villager B found a work block and got a job.
Villager A can no longer change jobs or replenish goods.
(The work block has not been destroyed during this period)
I don't know if this is a bug or a structured system.

There is no work block to the other around.
Work block is only one. However, two villagers are employed.
Also I saw the "effect" the villagers A loses occupation

 

I'm not good at English, but if you have a solution, please let me know.