So I was killing Gaia III for some grinding in one of our modpacks (Around 202 mods).
Then the Gaia III killed me but instead of dying I got an effect (Witches curse) and then I'm stuck in an infinite loop of dying.
I can walk around but not pick up items and open interfaces (Like chest or Me Systems) except inventory.
Nothing can kill me not even /Kill but because of some kind of bug or what ever the Sword of Cosmos does.

I have seen similar bug, but there are no Witches curse effect, just unkillable player.
We played on server, 1,12,2 version.
We managed to fix the problem via commands heal and then kill, but now we want to make new modpack and before using this awesome mod, I would like to find a normal solution.

As far as I remember, the /heal command fixed it
Maybe after that you need /kill.

Also I don't know exactly where this command comes from, since it seems to be non-vanilla
Upd. I did some search and now i think it is from FTB Essentials

I have seen similar bug, but there are no Witches curse effect, just unkillable player. We played on server, 1,12,2 version. We managed to fix the problem via commands heal and then kill, but now we want to make new modpack and before using this awesome mod, I would like to find a normal solution.

Excuse me, I have the same problem, could you tell me specifically how you managed to solve it and if you found a way to avoid it? Thanks in advance!!

I have seen similar bug, but there are no Witches curse effect, just unkillable player. We played on server, 1,12,2 version. We managed to fix the problem via commands heal and then kill, but now we want to make new modpack and before using this awesome mod, I would like to find a normal solution.

Excuse me, I have the same problem, could you tell me specifically how you managed to solve it and if you found a way to avoid it? Thanks in advance!!

As far as I remember, the /heal command fixed it Maybe after that you need /kill.

Also I don't know exactly where this command comes from, since it seems to be non-vanilla Upd. I did some search and now i think it is from FTB Essentials

I have seen similar bug, but there are no Witches curse effect, just unkillable player. We played on server, 1,12,2 version. We managed to fix the problem via commands heal and then kill, but now we want to make new modpack and before using this awesome mod, I would like to find a normal solution.

Excuse me, I have the same problem, could you tell me specifically how you managed to solve it and if you found a way to avoid it? Thanks in advance!!

Hmmm, I see, but I was looking and there is no ftb essential for 1.12.2, the mod is for 1.16.5 or higher and I can't find any other mod that adds the /heal command

As far as I remember, the /heal command fixed it Maybe after that you need /kill.
Also I don't know exactly where this command comes from, since it seems to be non-vanilla Upd. I did some search and now i think it is from FTB Essentials

I have seen similar bug, but there are no Witches curse effect, just unkillable player. We played on server, 1,12,2 version. We managed to fix the problem via commands heal and then kill, but now we want to make new modpack and before using this awesome mod, I would like to find a normal solution.

Excuse me, I have the same problem, could you tell me specifically how you managed to solve it and if you found a way to avoid it? Thanks in advance!!

Hmmm, I see, but I was looking and there is no ftb essential for 1.12.2, the mod is for 1.16.5 or higher and I can't find any other mod that adds the /heal command

i see...

i think MoreCommands mod (the red one) have heal command, but I sure that it is not the one I used before.
And maybe it is not a mod at all. I using server from AllTheMods team so maybe there some built in plugins i dont know

Upd.
Yeah, I found it, this time it seems to fit the version, the answer is FTB Utilities

I personally don't know why, but I think that because of some other mod that already uses the ID of the potion effect it shoots with that instead.

Actually it makes your HP value NaN (found out by using NBT explorer)