When you use zombie spawn egg to spawn baby zombies, the team label transmits wrongly.

Run the below command to spawn baby zombies, 

~~~

/give @s minecraft:zombie_spawn_egg[minecraft:entity_data=

] 64

~~~

When you /data to get team label of aldult zombies, it works and reveals "1",

but when you /data to get the Team label of the baby zombies, it's void.