Husks or zombies lose almost all of their NBT data when they convert into zombies or drowned mobs respectively.
How to reproduce
Use the command /summon husk ~ ~ ~ {DrownedConversionTime:100,Health:1.0} while underwater. Summoning a zombie also works.
The husk should have 1 health.
Wait 100 game ticks for the husk to convert into a zombie.
The zombie will have full health.
This affects almost all NBT. Some of the exceptions that I know of are armor, hand items, and custom names.
Linked issues
Comments 2
I do but I usually can't find the issue I'm looking for :<
Duplicate of MC-88967.
Please use the search function in the future, as there is a chance that your issue has already been reported.