When i execute a command like :

/attribute @p minecraft:generic.max_health base set 8

Command works but when player take heal or instant damage, there is a visual death bug.

It happen 100% of the time when the following condition are done :

• Player have all of he's base max health (20.0f)
• Run /attribute @p minecraft:generic.max_health base set 8
• Use /effect that change player amount heal points, use a potion that change player amount heal points, will cause the death bug

If the player don't have all of this base max health but something like 15.0f there is a little bug that decreasse health and up it (in 0.5 sec) at the max amount setted but no death bug.