Hi,

 

The spawnEntityIntoClientWorld() function in FMLClientHandler does not work properly for multi-part entities (Entity.getParts() != null).

 

entity.entityId will be set before the offsets are calculated for the parts. This leads to getEntityByID() in NetServerHandler always returning a wrong entity (or null in most cases) for those parts.

 

A simple solution is to move the assignment of the entity ID after the assignments of the parts' ids.

 

public Entity spawnEntityIntoClientWorld(EntityRegistration er, EntitySpawnPacket packet){
/*snip*/
            entity = (Entity)(cls.getConstructor(World.class).newInstance(wc));
            entity.entityId = packet.entityId;
/*snip*/
            Entity parts[] = entity.getParts();
            if (parts != null)
            {
                int i = packet.entityId - entity.entityId; //<- will always be 0
                for (int j = 0; j < parts.length; j++)
                {
                    parts[j].entityId += i;
                }
            }
/*snip*/
}

https://github.com/MinecraftForge/FML/commit/1642bad402efe819f4e763bf4b460d8c04194849