Healing mobs right as they die causes them to come back weirdly

Summary: If a mob dies and gets healed at the exact same frame, they start shaking weirdly in red. They cannot get killed again in this state.

How to reproduce (Warning: it doesn't work everytime, and there's other ways to reproduce too):

1. Summon a vindicator
2. Name the vindicator "Johnny"
3. Use the command: /effect @e[type=vindicator] resistance (any amount) 255 
4. If on 1.16.40, summon a zoglin. If on 1.16.100.55 beta, summon a horse.
5. On the frame before the zoglin/horse dies, throw a splash potion of healing II on the enemy

 Alternative Steps:

1. Have a repeating command block set to any tick delay with the command: /replaceitem entity @e[type=!player] slot.weapon.offhand 1 totem
2. Summon any mob in a cage (except for withers and ender dragons)
3. Ignite the floor the mob is standing with fire
4. As soon as the mob dies, do /kill on the mob you chosen

Observed Result: The mob shakes in a weird way in red and cannot get killed without (another) /kill.

Expected Result: A. The mob ignores the healing and dies, or B. The mob ignores death and comes back without the weird shaking and being red.

It works with most of the mobs, but some may require a different setup than others.

Edit of October 7th: I've attached a video that shows the glitched Zoglin as shown to give you a better understanding of this bug. Idk If this is WAI thou.