1.15.2 modded singleplayer world "Exception in server tick loop" error

[TielesitiEftu]

I can't get into my main survival world at the moment. This world is a singleplayer world running the latest Forge build for 1.15.2 at the time of this post being made (1.15.2 - 31.2.41), and I can't figure out what the issue is. I found another post on here from a few years ago (link here) that seems to cover a similar issue, but in all honesty, I don't understand a word of it since there's so much there for my brain to take in. Purely my own fault. Below is what happened when I realized something was up.

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I was playing the game when I noticed that everything had essentially frozen in time around me; a common thing for me that I now call The Edge or being Edged, so I did my usual strategy of using Task Manager to close the game (when Edged, the game processing is essentially unresponsive by now, so I have to use Task Manager) and reboot it a little bit later once everything's settled down some. Normally, this loads everything just fine (with some rollback). This time, however, I got a crash before the world loads, with this crash log being the one that seems to cover the most ground. The launcher's text is:

The game crashed whilst exception in server tick loop
Error: java.lang.IllegalArgumentException: Duplicate id value for 7!
Exit Code: -1

This persists every time I try to open this world. I have not tested other worlds to see if they have the same issue; in all honesty, it only occurred to me as I was writing this post, and I don't want to wait for fifteen minutes for a world to load so I can test it right now.

 

Somebody in a Discord server I'm in (not Minecraft- or Forge-focused, mind you, but there's some programmers in there) said that the "snowrealmagic" mod may be the cause. I tried booting without that mod, or its dependency "mixinbootstrap", but nothing changed; all that happened was their entries being removed from the end of the file. They also proposed the idea that "the mods used contain duplicated IDs of the same value. With the Exit Code being -1, it means there's two mods that aren't compatible with each other."

 

Can anyone help me out here?

[TielesitiEftu]

Huh. Alright, gotta admit, was not expecting that one to be the problem. I don't think I have the courage to say something like That to the dev, but I'll mention this in the comments. Let me see how the world works out if I get rid of that mod, and I'll get back to you on how this goes.

[TielesitiEftu]

ngl I had this thread open and the reply notification noise made me jump a little bit-
I will. I'm booting up Minecraft now; I've quarantined the mod so I can test this out.

 

Edit 4:07 AM: Success! I can once again access the world. Thanks a bunch!

Edited September 25, 2020 by TielesitiEftu
I just didn't wanna double comment lmao