Affected Mod Versions:

• Forge version: forge-1.12.2-14.23.5.2838.jar (universal installer for server
• RTG version: RTG-1.12.2-6.1.0.0-snapshot.1.jar

Other mods:

• BetterDiving-1.12.2-1.4.14
• Chisel-MC1.12.2-0.2.1.35
• CoralReef-2.5-1.12.2
• CTM-MC1.12.2-1.0.1.30
• CustomMobSpawner-3.11.5
• DrZharks MoCreatures Mod-12.0.5
• Ecnanos'+More+Armor++Tools+Mod+[1.12.2]+{1.3.2}
• levelup2-1.2.4
• Mantle-1.12-1.3.3.55
• MineTraps-1.12.2-(v.1.0.4)
• Rex's-Additional-Structures-1.12.x-(v.2.3.1)
• TConstruct-1.12.2-2.10.1.87
• TinkerToolLeveling-1.12.2-1.1.0
• Trapcraft-1.12-v2.4.3a-universal
• u_team_core-1.12.2-2.2.5.147
• useful_backpacks-1.12.2-1.5.3.59

Issue Description:

https://pastebin.com/FMKMtzTp

Steps to reproduce the issue: (If it's easily reproducible.)

Not sure if it's easy to reproduce, It's happend when launching my modded server

Extra Information:

https://pastebin.com/BzvLbHp9

[20:23:58] [Server thread/WARN] [FML]: Zip file RTG-1.12.2-6.1.0.0-snapshot.1.jar failed to read properly, it will be ignored

You probably have a corrupt jar. Redownload the mod from: https://www.curseforge.com/minecraft/mc-mods/realistic-terrain-generation/download/2782568