using damage(amount,entity) from https://hub.spigotmc.org/javadocs/spigot/org/bukkit/entity/Damageable.html there is a clientside bug, if the damaged player has ABSORPTION effect active yellow hearths do not get any update, and will last even after death until an update is given (ex: applying again absorbition effect)

on the video (sorry was made by cell) the player is hitted using damage(...) yellow hearths wont change as showed