Program: 156321
Project: 156321
Buggy source:
@Override public void renderTileEntityAt(TileTank tile,double x,double y,double z,float partialTicks,int destroyStage){
  FluidStack forRender=tile.tank.getFluidForRender();
  if (forRender == null) {
    return;
  }
  Minecraft.getMinecraft().mcProfiler.startSection("String_Node_Str");
  Minecraft.getMinecraft().mcProfiler.startSection("String_Node_Str");
  RenderHelper.disableStandardItemLighting();
  Minecraft.getMinecraft().getTextureManager().bindTexture(TextureMap.LOCATION_BLOCKS_TEXTURE);
  GlStateManager.enableBlend();
  GlStateManager.blendFunc(SourceFactor.SRC_ALPHA,DestFactor.ONE_MINUS_SRC_ALPHA);
  VertexBuffer vb=Tessellator.getInstance().getBuffer();
  vb.begin(GL11.GL_QUADS,DefaultVertexFormats.BLOCK);
  vb.setTranslation(x,y,z);
  boolean[] sideRender={true,true,true,true,true,true};
  boolean connectedUp=isFullyConnected(tile,EnumFacing.UP);
  boolean connectedDown=isFullyConnected(tile,EnumFacing.DOWN);
  sideRender[EnumFacing.DOWN.ordinal()]=!connectedDown;
  sideRender[EnumFacing.UP.ordinal()]=!connectedUp;
  Vec3d min=connectedDown ? MIN_CONNECTED : MIN;
  Vec3d max=connectedUp ? MAX_CONNECTED : MAX;
  int blocklight=forRender.getFluid().getLuminosity(forRender);
  int combinedLight=tile.getWorld().getCombinedLight(tile.getPos(),blocklight);
  FluidRenderer.vertex.lighti(combinedLight);
  FluidRenderer.renderFluid(FluidSpriteType.STILL,forRender,tile.getFluidAmountForRender(partialTicks),tile.tank.getCapacity(),min,max,vb,sideRender);
  vb.setTranslation(0,0,0);
  Tessellator.getInstance().draw();
  RenderHelper.enableStandardItemLighting();
  Minecraft.getMinecraft().mcProfiler.endSection();
  Minecraft.getMinecraft().mcProfiler.endSection();
}

Fixed version (ground truth):
@Override public void renderTileEntityAt(TileTank tile,double x,double y,double z,float partialTicks,int destroyStage){
  SmoothedFluid forRender=tile.getFluidForRender(partialTicks);
  if (forRender == null) {
    return;
  }
  Minecraft.getMinecraft().mcProfiler.startSection("String_Node_Str");
  Minecraft.getMinecraft().mcProfiler.startSection("String_Node_Str");
  RenderHelper.disableStandardItemLighting();
  Minecraft.getMinecraft().getTextureManager().bindTexture(TextureMap.LOCATION_BLOCKS_TEXTURE);
  GlStateManager.enableBlend();
  GlStateManager.blendFunc(SourceFactor.SRC_ALPHA,DestFactor.ONE_MINUS_SRC_ALPHA);
  VertexBuffer vb=Tessellator.getInstance().getBuffer();
  vb.begin(GL11.GL_QUADS,DefaultVertexFormats.BLOCK);
  vb.setTranslation(x,y,z);
  boolean[] sideRender={true,true,true,true,true,true};
  boolean connectedUp=isFullyConnected(tile,EnumFacing.UP);
  boolean connectedDown=isFullyConnected(tile,EnumFacing.DOWN);
  sideRender[EnumFacing.DOWN.ordinal()]=!connectedDown;
  sideRender[EnumFacing.UP.ordinal()]=!connectedUp;
  Vec3d min=connectedDown ? MIN_CONNECTED : MIN;
  Vec3d max=connectedUp ? MAX_CONNECTED : MAX;
  FluidStack fluid=forRender.fluid;
  int blocklight=fluid.getFluid().getLuminosity(fluid);
  int combinedLight=tile.getWorld().getCombinedLight(tile.getPos(),blocklight);
  FluidRenderer.vertex.lighti(combinedLight);
  FluidRenderer.renderFluid(FluidSpriteType.STILL,fluid,forRender.amount,tile.tank.getCapacity(),min,max,vb,sideRender);
  vb.setTranslation(0,0,0);
  Tessellator.getInstance().draw();
  RenderHelper.enableStandardItemLighting();
  Minecraft.getMinecraft().mcProfiler.endSection();
  Minecraft.getMinecraft().mcProfiler.endSection();
}