This mod seems to cause skeletons without AI to spawn randomly in the world. They don't burn in the sunlight, and once you hit them once, they stop doing damage animations as well. They just kinda stand there and don't do anything. It might be an interaction with another mod, but I really have no idea. No crash report. Sorry if this isn't very helpful. :\

Forge is version 14.23.5.2847. Modlist here:
https://pastebin.com/86rmSp3v

@TaoismDeepLake That's an older version of Optifine, can you please try to fix it with the version OptiFine HD U G5

@DeviceGucci So it only works on older optifines? If updating optifine fixes it, there's no point in making a fix mod.

@TaoismDeepLake Updating optifine does not fix it, and I can't run the version of optifine that you mentioned because it crashes my game. The fix is required on newer versions, but maybe not on older versions, hopefully someone can fix this

i really hope this gets fixed soon, it's such a must-have mod!

just noticed how old this problem is, truly a shame...

I also encountered these skeletons
I was also wondering which mod is causing this problem (because of having around 200 mods it's a bit tiring)
appear in my village and cause chaos in the villagers it starts to lead me to solve this problem because guards with bows will kill themselves with them. Personally, it doesn't bother me, I just need to take one arrow or hit this skeleton with a sword or bow with a lot of ~30 damage and at least I have bones but as I wrote above, the guards will kill each other because of them

It's an issue caused by older versions of optifine. Other mods have the same issue.

Let me tell you.
Check your BetterSpiderEntity.java of 1.12.2
` @OverRide
@nullable
public IEntityLivingData onInitialSpawn(DifficultyInstance difficulty, @nullable IEntityLivingData data) {
data = super.onInitialSpawn(difficulty, data);

	if(this.world.rand.nextInt(100) == 0) {
		EntitySkeleton skeleton = new EntitySkeleton(this.world);
		skeleton.setLocationAndAngles(this.posX, this.posY, this.posZ, this.rotationYaw, 0.0F);
		skeleton.onInitialSpawn(difficulty, (IEntityLivingData)null);
		this.world.spawnEntity(skeleton);
		skeleton.startRiding(this);
	}`

You did not check whether the world is remote. If these code execute in remote world, you will get those no-ai skeletons. Consider fixing this in 1.12.2.

@TheCyberBrick A CN player metioned this bug, too. I looked up your code and find the possible solution as above. Please consider patching it if you have the time. Already made a PR.

This has been happening to me as well so I'm uploading my modpack here

I can confirm.

Forge 2854

And compared to ekiplier's list above ... these are the mods we have in common ...

BetterFPS
Born in a Barn
Dynamic Trees
Creative Core
Forgelin
Better Foliage
Optifine
Better Animals
VanillaFix

I was wondering the exact same thing the other day so now I can confirm.

Forge 2847

Running most of the mods listed by ekiplier and all of the ones listed by Dvoric except for BetterFPS and Dynamic Trees.
Meaning we have these in common:

1. Born in a Barn
2. Creative Core
3. Forgelin
4. Better Foliage
5. Optifine
6. Better Animals
7. VanillaFix

Full list just in case:
https://pastebin.com/zgRcz16D

Update: So apparently uninstalling optifine fixes the issue, which is weird because, you know, it's optifine. Also, nothing seems to manifest itself in the logs. Maybe there's something in the options menu we should look out for?

https://github.com/TaoismDeepLake/spider2fix2/releases/tag/1.1

For those who can't wait for the official fix, install my fix mod alongside.

It is reported that my fix mod doesnot work. I will do some further trials, though an official build works the best.

I cannot reproduce this bug from the very beginning. I just provided a theortical fix.
I tried installing optifineE2 yet I see no fail-skeleton. If anybody can provide more information, you are welcomed. I will try another time soon.