Uh, wut? Is it not normal minecraft server code?!
You can disable that ASM via the asm config file that gets created on launch, just look at the file asm.ini file in the config/gregtech directory and change:
transformer:gregtech.asm.transformers.Minecraft_MinecraftServerIntegratedLaunchMainMenuPartialFix = true
To be:
transformer:gregtech.asm.transformers.Minecraft_MinecraftServerIntegratedLaunchMainMenuPartialFix = false
In other words just set it false on the server.
That’s very oddly questionable though, all that asm does is change a 0 to 40, so that’s really odd…
Also, java should be printing out class bytecode information if there is such a crash, if you can find that and give it here then I might be able to fix it.