[1.10.2] MultiLayerModel only adds first .obj to the IModelState parts list

public class PipeBasic extends BlockGenericPipe implements ITileEntityProvider{

public PipeBasic() {
	super(Material.IRON);
	setUnlocalizedName(References.NAME_PIPE_BASIC);
	setRegistryName(References.RN_PIPE_BASIC);
	setCreativeTab(CreativeTabs.TRANSPORTATION);

}

@Override
@SideOnly(Side.CLIENT)
public void initModel() {
	ModelLoader.setCustomModelResourceLocation(Item.getItemFromBlock(this), 0, new ModelResourceLocation(getRegistryName(), "inventory"));

}

@Override
public IBlockState getExtendedState(IBlockState state, IBlockAccess world, BlockPos pos) {
	if(world.getTileEntity(pos) != null && world.getTileEntity(pos) instanceof TileBasicPipe) {
		TileBasicPipe te = (TileBasicPipe)world.getTileEntity(pos);
		te.checkConnections(world, pos);
		return ((IExtendedBlockState) state).withProperty(Properties.AnimationProperty, te.state);
	}
	return state;
}

@Override
public boolean canRenderInLayer(BlockRenderLayer layer) {
	return layer == BlockRenderLayer.SOLID || layer == BlockRenderLayer.TRANSLUCENT;
}

@Override
@SideOnly(Side.CLIENT)
public boolean shouldSideBeRendered(IBlockState blockState, IBlockAccess worldIn, BlockPos pos, EnumFacing side) {return false;}

@Override
public boolean isBlockNormalCube(IBlockState state) {return false;}

@Override
    public boolean isFullCube(IBlockState state) { return false; }

@Override
public boolean isOpaqueCube(IBlockState state) {return false;}

@Override
    public boolean isVisuallyOpaque() { return false; }

@Override
public int getMetaFromState(IBlockState state) {return 0;}

@Override
public boolean hasTileEntity() {return true;}

@Override
public TileEntity createNewTileEntity(World worldIn, int meta) {
	return new TileBasicPipe();
}

@Override
public BlockStateContainer createBlockState() {
	return new ExtendedBlockState(this, new IProperty[0], new IUnlistedProperty[] {Properties.AnimationProperty});
}

}

public class TileBasicPipe extends TileEntity implements IRoutable, IPipe{

private boolean hasChanged = false;

private final List<String> hidden = new ArrayList<String>();
public final IModelState state = new IModelState()
{
	private final Optional<TRSRTransformation> value = Optional.of(TRSRTransformation.identity());

	@Override
	public Optional<TRSRTransformation> apply(Optional<? extends IModelPart> part)
        {
            if(part.isPresent())
            {
                // This whole thing is subject to change, but should do for now.
                UnmodifiableIterator<String> parts = Models.getParts(part.get());
                if(parts.hasNext())
                {
                    String name = parts.next();
                    // only interested in the root level
                    if(!parts.hasNext() && hidden.contains(name))
                    {
                        return value;
                    }
                }
            }
            return Optional.absent();
        }

};


@Override
public NBTTagCompound getUpdateTag() {return writeToNBT(new NBTTagCompound());}

@Override
public SPacketUpdateTileEntity getUpdatePacket() {
	NBTTagCompound nbtTag = new NBTTagCompound();
	this.writeToNBT(nbtTag);
	return new SPacketUpdateTileEntity(getPos(), 1, nbtTag);
}

@Override
    public void onDataPacket(NetworkManager net, SPacketUpdateTileEntity packet) {
        this.readFromNBT(packet.getNbtCompound());
    }

@Override
    public void readFromNBT(NBTTagCompound compound) {super.readFromNBT(compound);}

@Override
    public NBTTagCompound writeToNBT(NBTTagCompound compound) {
        super.writeToNBT(compound);
        
        return compound;
    }

public void checkConnections(IBlockAccess world, BlockPos pos) {
	ArrayList<String> check = ConnectionHelper.checkForPipes(world, pos);

	if(!hidden.equals(check)) {
		hasChanged=true;
		hidden.clear();
		for(String s : check) {
			hidden.add(s);
		}
	}

	updateBlock();

}

private IBlockState getState() {
	return worldObj.getBlockState(pos);
}

public void updateBlock(){
	if(hasChanged){
		this.worldObj.markBlockRangeForRenderUpdate(this.pos, this.pos);
		this.worldObj.notifyBlockUpdate(pos, getState(), getState(), 3);
		this.worldObj.scheduleBlockUpdate(this.pos, this.getBlockType(), 0, 0);

		markDirty();
		hasChanged=false;
	}
}

@Override
public boolean isRouted() {return false;}

@Override
public boolean isRoutable() {return true;}

@Override
public boolean hasNetwork() {return false;}

@Override
public boolean hasPower() {return false;}

@Override
public boolean consumesPower() {return false;}

@Override
public int powerConsumed() {return 0;}

}

The ConnectionHelper.checkPipes() method checks all 6 directions for a Pipe and returns a List of Strings resembling the Model Parts(Solid and Glas Part of each connection) to be hidden. If a change is detected by the Tile, it clears its old hidden list and inserts the new Values.

{
  "forge_marker": 1,
  "defaults": {
    "model": "forge:multi-layer",
    "transform": "forge:default-block",
    "custom": {
    	"base": "lptwo:pipe_basic#normal",
    	"Solid": "lptwo:pipe_basic#normal",
    	"Translucent": "lptwo:pipe_basic#glass"
    }
  },
  "variants": {
    "normal": [{
    	"model": "lptwo:pipe_basic.obj",
    	"custom": {"flip-v": true}
    }],
    "glass": [{
    	"model": "lptwo:pipe_glass.obj",
    	"custom": {"flip-v": true}
    }],
    "inventory": [{}]
  }
}