throwawaymodder

I'm running into an odd issue when right-clicking a custom tile entity to open its container on a server, and no amount of Googling has brought me to a solution. It all works fine in singleplayer, but on a server, no GUI appears, and instead this is logged in the client's debug.log: Neither the server nor the client crashes, and nothing is logged on the server. Here's the relevant code: PackageBlock.Java: public class PackageBlock extends ContainerBlock { ... @Override public ActionResultType onBlockActivated(BlockState state, World world, BlockPos pos, PlayerEntity player, Hand hand, BlockRayTraceResult hit) { ... if (!world.isRemote()) { ... TileEntity te = world.getTileEntity(pos); if (te != null && te instanceof PackageTileEntity) { NetworkHooks.openGui((ServerPlayerEntity) player, (PackageTileEntity) te); } return ActionResultType.SUCCESS; } } } PackageTileEntity.java public class PackageTileEntity extends TileEntity implements IInventory, INamedContainerProvider { ... @Override public Container createMenu(int windowId, PlayerInventory playerInventory, PlayerEntity player) { return new PackageContainer(windowId, playerInventory, this); } ... } PackageContainer.java public class PackageContainer extends Container implements INameable { public PackageContainer(int windowId, PlayerInventory playerInventory) { this(windowId, playerInventory, new Inventory(PackageBlock.INVENTORY_SIZE)); } public PackageContainer(int windowId, PlayerInventory playerInventory, IInventory packageInventory) { super(EnderMailContainers.PACKAGE_CONTAINER, windowId); this.packageInventory = packageInventory; packageInventory.openInventory(playerInventory.player); ...<add slots>... } ... } EnderMailContainers.java @EventBusSubscriber(bus = EventBusSubscriber.Bus.MOD) @ObjectHolder(EnderMail.MODID) public class EnderMailContainers { @ObjectHolder(PackageContainer.NAME) public static final ContainerType<PackageContainer> PACKAGE_CONTAINER = null; @SubscribeEvent public static void onContainerTypeRegistry(final RegistryEvent.Register<ContainerType<?>> event) { event.getRegistry().register(new ContainerType<>(PackageContainer::new).setRegistryName(PackageContainer.NAME)); } } EnderMail.java public void clientInit(FMLClientSetupEvent event) { ... ScreenManager.registerFactory(EnderMailContainers.PACKAGE_CONTAINER, PackageScreen::new); } The entirety of the source code can be found here, if it's needed. Things I've tried: Using player.openContainer instead of NetworkHooks.openGui in PackageBlock.java. The result was the same, except that the player was kicked off the server with a similar error message appearing on the screen before returning to the multiplayer menu: "Internal Exception: io.netty.handler.codec.DecoderException:com.google.gson.JsonParseException: Don't know how to turn {} into a Component." The error logged in debug.log was identical, and nothing was logged on the server. Passing a PacketBuffer argument with the NetworkHooks.openGui call. Same result. Thanks in advance for the help.