[1.21.1]

[homosapien97]

Base information

• Minecraft version: 1.21
• Mod version: 3.1.4.630
• Minecraft Forge version: neoforge 21.1.219
• Mod Pack: All the Mods 10 5.5

Description / steps to reproduce

Short description: using mob grinder on certain mobs sets them to 0 health (but still there) and unkillable. When the player attacks these mobs the player's health is also set to 0, but the player does not die either, just gets a lot of screenshake and inventory closes immediately upon opening.

More details: the mob in question is a pillager spawned from an apotheosis mob spawner with a few modifications like NoAI and lower starting health. It looks like all the bugged mobs are Apotheosis bosses (they have backpacks on, potion effects, and a lot of health. I believe this is caused by Apotheosis). The reason I am filing this bug here instead of on Apotheosis is that other methods of killing these mobs do not result in this glitch. When I was killing them by hand (before creating any glitched mobs), this did not happen. When killing with the mob masher from mob grinding utils, this did not happen either. I only started getting the glitched zero-health boss pillagers after using the mob grinder.
The machine settings: Show AOE, Collect Items, filter for any of: forbidden_arcanus:corrupt_lost_soul, forbidden_arcanus:enchanted_lost_soul, hostile mobs only. The machine has an unobtainium sword in it, with Soul Looting VI on it. The location this is happening is in the mining dimension.

I was able to repro this in a creative world.
Steps:
-Create a creative world in ATM 10 5.5
-Place down an empty apothic spawner
-Right Click on it with a pillager spawn egg
-Right click on it with enough dripstone to get it down to 20% starting health
-Right click on it with a nether star
-Right click on it with a chorus fruit
-Right click on it with a piece of wool
-Right click on it with as much sugar and clocks as it will take
-Place down a mob grinder pointing at it with a creative energy cell or something

I don't know which of these steps is important, but i suspect it is something to do with lowering the starting health + some weird apotheosis boss mob effect + the way that the draconic grinder kills things.

EDIT: the weird mobs are all wearing Sophisticated Backpacks backpacks, so they might be spawned by that mod instead of Apotheosis

Here is a screenshot:

[DEVilInCode]

I have the same problem. I also noticed that this bug only affects mobs that can wear any armor and was spawned with it. (If i'm not mistaken, in my case it works even without any backpacks)

• Pretty often works on: zombie, skeleton
• Not works on: creeper, enderman, etc

[homosapien97]

Interesting that it happens for all armored mobs for you--I was able to work around the issue on my end by disabling SophisticatedBackpacks elite mobs in its config, and have not seen the issue since. Maybe I just got lucky and my pillager spawner doesn't make armored mobs

[DEVilInCode]

Like i said. Zombie without any backpack. Just armor.
First one was naturally spawned. Second one - from spawner
I could say even more, mobs with backpacks pretty easy died from mob grinder

[thisis789]

Had this happen on my custom pack aswell. Nothing involving backpacks for me. was spawning blaze and endermen with enderio powered spawners.

none of them had backpacks or armor just vanilla. about 8 mobs total in the grinder room before i realized what was going on. had 0 hearts but were not dead, could not be killed with "/kill @e" had to drop them into the void.

a blaze hit me and corrupted my player. Had to delete my playerdata from server files.

Ver: 1.21.1-3.1.4.632