All other weapons work fine.
It's only chaotic weaponry that throw this missing opcode error.
Spoiler for error:
Any idea where to look lolCode:public int getCombatOpcode(int opcode) {
Integer value = (Integer) clientScriptData.get(opcode);
if (value != null)
return value;
GeneralRequirementMap map = getCombatMap();
return map == null ? 0 : map.getIntValue(opcode);
}