Zombie Villagers do not zombify other villagers 100% of the time in hard mode

Summary:
Unemployed villagers do not always turn into zombie villagers when attacked by a zombie villager in Hard mode.

Steps to Reproduce:

1. Spawn multiple villagers in a small room
2. Make sure all of the villagers are unemployed
3. Set the difficulty to Hard
4. Spawn a zombie villager in the room

Observed Results:
Some of the villagers die.

Expected Results:
The villagers should always turn into zombie villagers.

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Original Description:
In hard mode, the zombification chance is supposed to be 100%. This is true for normal zombies attacking villagers, but not for zombie villagers attacking villagers. They can die without getting zombified. I tested this in a chamber with one normal zombie and many villagers. The normal zombie turns villagers into zombie villagers, but the zombie villagers created from this have a chance of killing other villagers.