Basics:

• Minecraft Version: 1.12.2
• Mod Version: (newest) incontrol-1.12-3.9.18

Description:

The first Attack that a player makes against an entity with lower then vanilla default HP get ignored
Note: Knockback applies as usual, but damage does not
Note 2: When using a HUD Mod and attack the entity, the number "19" pops out (when punching an zombie for example) PIC: I.IMGUR

Reproduce Bug:

• Get a fresh 1.12.2 Minecraft Version
• Drop InControl in the mod folder (and no other mods)
• Use this script in "spawn.json" | PAST BIN Version: https://pastebin.com/fYS5Vy1b
  [
  {
  "result": "default",
  "nbt": {
  "Attributes": [
  {
  "Base": 0,
  "Modifiers": [
  {
  "Operation": 0,
  "Amount": 0.1,
  "Name": "effect.maxhealth 0"
  }
  ],
  "Name": "generic.maxhealth"
  }
  ]
  }
  }
  ]
• Take a Diamond Axe and attack an entity spawn nearby at night

What I test so far:

• "onjoin" - true/false/deleted from script
• When close Minecraft, delete the Script and restart -> all mobs nearby can get killed with one punch (so the extra blow to calculate the true HP value is not necessary any more)
• Set values from "0.1" to "1"

What "I" think

• Maybe the Mob HP don't get refreshed when spawning the first time in the world

Maybe more Testing:

• What if Health set higher then 20 HP? Will it be the same bug?

Goal

I need to set HP Values for Mobs to an exact value. So I can enable nice balanced values between Weapon Damage and how many blows it takes to kill a mob in a given DIM / Y Layer.

More Testing:

• When Cows get hit (by Hand), they take 9 Damage and update there life (cows have 10 HP in vanilla)
• When using Wither effect, all Mobs HP get updated (/effect @e minecraft:wither 2 0)
• Instant Damage Splash Potion has the same effect like wither

Mod get no longer Supported for 1.12.2, so this Bug will still there and will not get debuged.
Workaround: Give Mobs a "wither" potion effect for 2 seconds. This will refresh the HP of the mob.
There is no good solution to this bug at the given state.

Discord Chat: https://discord.com/channels/403871125206990849/647450546617319434/806214040350752768

More Testing:

• When "onjoin" = true and /gamerule doMobSpawn = false, animals spawn and can be killed with one hit (no HP refresh needed)
• When "onjoin" = true = mob eggs spawning works fine (one hit)
• When "onjoin" = true and /summon minecraft:zombie used, HP are NOT updated (so a HP refresher is needed)