Program: 156369
Project: 156369
Buggy source:
/** 
 * Used to render a lot of items in sequential order. Assumes that you don't change the glstate inbetween calls. You must call   {@link #endItemBatch()} after your have rendered all of the items. 
 */
public static void renderItemStack(double x,double y,double z,ItemStack stack,EnumFacing dir,VertexBuffer vb){
  if (stack.isEmpty()) {
    return;
  }
  if (dir == null) {
    dir=EnumFacing.EAST;
  }
  dir=BCLibConfig.rotateTravelingItems.changeFacing(dir);
  IBakedModel model=Minecraft.getMinecraft().getRenderItem().getItemModelMesher().getItemModel(stack);
  model=model.getOverrides().handleItemState(model,stack,null,null);
  boolean requireGl=stack.hasEffect() || model.isBuiltInRenderer();
  if (vb != null && !requireGl) {
    vb.setTranslation(x,y,z);
    float scale=0.30f;
    MutableQuad q=new MutableQuad(-1,null);
    for (    EnumPipePart part : EnumPipePart.VALUES) {
      for (      BakedQuad quad : model.getQuads(null,part.face,0)) {
        q.fromBakedItem(quad);
        q.translated(-0.5,-0.5,-0.5);
        q.scaled(scale);
switch (dir) {
case EAST:
{
            q.rotateY_90(1);
            break;
          }
case WEST:
{
          q.rotateY_90(-1);
          break;
        }
case DOWN:
{
        q.rotateX_90(1);
        break;
      }
case UP:
{
      q.rotateX_90(-1);
      break;
    }
case NORTH:
{
    q.rotateY_180();
    break;
  }
case SOUTH:
{
  break;
}
default :
{
throw new IllegalStateException("String_Node_Str" + dir);
}
}
if (quad.hasTintIndex()) {
int colour=Minecraft.getMinecraft().getItemColors().getColorFromItemstack(stack,quad.getTintIndex());
if (EntityRenderer.anaglyphEnable) {
colour=TextureUtil.anaglyphColor(colour);
}
q.multColouri(colour,colour >> 8,colour >> 16,0xFF);
}
q.lighti(15,15);
Vector3f normal=q.getCalculatedNormal();
q.normalvf(normal);
q.multShade();
q.render(vb);
}
}
vb.setTranslation(0,0,0);
return;
}
if (!inBatch) {
inBatch=true;
Minecraft.getMinecraft().renderEngine.bindTexture(TextureMap.LOCATION_BLOCKS_TEXTURE);
}
}

Fixed version (ground truth):
/** 
 * Used to render a lot of items in sequential order. Assumes that you don't change the glstate inbetween calls. You must call   {@link #endItemBatch()} after your have rendered all of the items. 
 */
public static void renderItemStack(double x,double y,double z,ItemStack stack,int lightc,EnumFacing dir,VertexBuffer vb){
  if (stack.isEmpty()) {
    return;
  }
  if (dir == null) {
    dir=EnumFacing.EAST;
  }
  dir=BCLibConfig.rotateTravelingItems.changeFacing(dir);
  IBakedModel model=Minecraft.getMinecraft().getRenderItem().getItemModelMesher().getItemModel(stack);
  model=model.getOverrides().handleItemState(model,stack,null,null);
  boolean requireGl=stack.hasEffect() || model.isBuiltInRenderer();
  if (vb != null && !requireGl) {
    vb.setTranslation(x,y,z);
    float scale=0.30f;
    MutableQuad q=new MutableQuad(-1,null);
    for (    EnumPipePart part : EnumPipePart.VALUES) {
      for (      BakedQuad quad : model.getQuads(null,part.face,0)) {
        q.fromBakedItem(quad);
        q.translated(-0.5,-0.5,-0.5);
        q.scaled(scale);
switch (dir) {
case EAST:
{
            q.rotateY_90(1);
            break;
          }
case WEST:
{
          q.rotateY_90(-1);
          break;
        }
case DOWN:
{
        q.rotateX_90(1);
        break;
      }
case UP:
{
      q.rotateX_90(-1);
      break;
    }
case NORTH:
{
    q.rotateY_180();
    break;
  }
case SOUTH:
{
  break;
}
default :
{
throw new IllegalStateException("String_Node_Str" + dir);
}
}
if (quad.hasTintIndex()) {
int colour=Minecraft.getMinecraft().getItemColors().getColorFromItemstack(stack,quad.getTintIndex());
if (EntityRenderer.anaglyphEnable) {
colour=TextureUtil.anaglyphColor(colour);
}
q.multColouri(colour,colour >> 8,colour >> 16,0xFF);
}
q.lighti(lightc);
Vector3f normal=q.getCalculatedNormal();
q.normalvf(normal);
q.multShade();
q.render(vb);
}
}
vb.setTranslation(0,0,0);
return;
}
if (!inBatch) {
inBatch=true;
Minecraft.getMinecraft().renderEngine.bindTexture(TextureMap.LOCATION_BLOCKS_TEXTURE);
}
}