Minecraft version & Mod Version:
1.12.2 & RootsClassic-1.12.2-1.1.5

Single player or Server:
Server

Describe problem (what you were doing / what happened):
I attempted to use CraftTweaker2 to change the recipe of a Roots Classic spell. The script I wrote works in singleplayer, but upon attempting to implement it on a server, it failed. According to the logs, one of the mods involved is trying to call client code, rather than server code. Another test script for CraftTweaker2 that did not reference Roots Classic worked fine, so I assume the latter is where the problem lies.

Crash log (if any):
Not a crash, but:

[INITIALIZATION][SERVER][ERROR] [crafttweaker]: Error executing {[0:crafttweaker]: shatter.zs}: net/minecraft/client/resources/I18n
java.lang.NoClassDefFoundError: net/minecraft/client/resources/I18n
at elucent.rootsclassic.component.ComponentRecipe.getLocalizedName(ComponentRecipe.java:24)
at elucent.rootsclassic.compat.SpellZen.setSpellItems(SpellZen.java:31)
at Shatter.script(shatter.zs:4)
at ZenMain.run(Shatter)
at crafttweaker.runtime.CrTTweaker.loadScript(CrTTweaker.java:221)
at crafttweaker.runtime.CrTTweaker.loadScript(CrTTweaker.java:101)
at crafttweaker.mc1120.events.CommonEventHandler.registerRecipes(CommonEventHandler.java:69)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_159_CommonEventHandler_registerRecipes_Register.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus$1.invoke(EventBus.java:144)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
at net.minecraftforge.registries.GameData.fireRegistryEvents(GameData.java:762)
at net.minecraftforge.common.crafting.CraftingHelper.loadRecipes(CraftingHelper.java:623)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:742)
at net.minecraftforge.fml.server.FMLServerHandler.finishServerLoading(FMLServerHandler.java:108)
at net.minecraftforge.fml.common.FMLCommonHandler.onServerStarted(FMLCommonHandler.java:338)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:219)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:486)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.resources.I18n
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 19 more
Caused by: java.lang.NullPointerException

(If this is a suggestion and not a bug report, delete all this and just write your suggestion!)