I noticed that baby chickens that grow up will not die in an automatic chicken cooker until the game is restarted.

To reproduce:

• Spawn a baby chicken in a 1x1 space, on a bottom half slab, with lava above
• Wait 20 minutes until the chicken grows
• Notice that the adult chicken is now within the lava above, but not dying
• Restart the world and the chicken should then die instantly

This only happens if the young chickens grow in the lava, spawning in adult chickens causes them to die instantly.

See picture for reference.

This reportedly happens with other mobs that grow too.