Program: 81850
Project: 81850
Buggy source:
@SubscribeEvent @SideOnly(Side.CLIENT) public void onScreenEvent(RenderGameOverlayEvent.Pre event){
  if (false && event.getType() == RenderGameOverlayEvent.ElementType.ALL) {
    Minecraft mc=Minecraft.getMinecraft();
    float lightLevel=0.4F;
    lightLevel=MathHelper.clamp(lightLevel,0.0F,1.0F);
    WorldBorder worldborder=mc.world.getWorldBorder();
    float f=(float)worldborder.getClosestDistance(mc.player);
    double d0=Math.min(worldborder.getResizeSpeed() * (double)worldborder.getWarningTime() * 1000.0D,Math.abs(worldborder.getTargetSize() - worldborder.getDiameter()));
    double d1=Math.max((double)worldborder.getWarningDistance(),d0);
    if ((double)f < d1) {
      f=1.0F - (float)((double)f / d1);
    }
 else {
      f=0.0F;
    }
    float prevVignetteBrightness=lightLevel;
    GlStateManager.disableDepth();
    GlStateManager.depthMask(false);
    GlStateManager.tryBlendFuncSeparate(GlStateManager.SourceFactor.ZERO,GlStateManager.DestFactor.ONE_MINUS_SRC_COLOR,GlStateManager.SourceFactor.ONE,GlStateManager.DestFactor.ZERO);
    if (f > 0.0F) {
      GlStateManager.color(0.0F,f,f,1.0F);
    }
 else {
      GlStateManager.color(prevVignetteBrightness,prevVignetteBrightness,prevVignetteBrightness,1.0F);
    }
    ScaledResolution scaledRes=new ScaledResolution(mc);
    GlStateManager.enableBlend();
    mc.getTextureManager().bindTexture(new ResourceLocation("String_Node_Str"));
    Tessellator tessellator=Tessellator.getInstance();
    VertexBuffer vertexbuffer=tessellator.getBuffer();
    vertexbuffer.begin(7,DefaultVertexFormats.POSITION_TEX);
    vertexbuffer.pos(0.0D,(double)scaledRes.getScaledHeight() * scaledRes.getScaleFactor() * 1D,-90.0D).tex(0.0D,1.0D).endVertex();
    vertexbuffer.pos((double)scaledRes.getScaledWidth() * scaledRes.getScaleFactor(),(double)scaledRes.getScaledHeight() * scaledRes.getScaleFactor(),-90.0D).tex(1.0D,1.0D).endVertex();
    vertexbuffer.pos((double)scaledRes.getScaledWidth() * scaledRes.getScaleFactor(),0.0D,-90.0D).tex(1.0D,0.0D).endVertex();
    vertexbuffer.pos(0.0D,0.0D,-90.0D).tex(0.0D,0.0D).endVertex();
    tessellator.draw();
    GlStateManager.depthMask(true);
    GlStateManager.enableDepth();
    GlStateManager.color(1.0F,1.0F,1.0F,1.0F);
    GlStateManager.tryBlendFuncSeparate(GlStateManager.SourceFactor.SRC_ALPHA,GlStateManager.DestFactor.ONE_MINUS_SRC_ALPHA,GlStateManager.SourceFactor.ONE,GlStateManager.DestFactor.ZERO);
  }
}

Fixed version (ground truth):
@SubscribeEvent @SideOnly(Side.CLIENT) public void onScreenEvent(RenderGameOverlayEvent.Pre event){
  if (false && event.getType() == RenderGameOverlayEvent.ElementType.ALL) {
    Minecraft mc=Minecraft.getMinecraft();
    float lightLevel=0.4F;
    lightLevel=MathHelper.clamp(lightLevel,0.0F,1.0F);
    WorldBorder worldborder=mc.world.getWorldBorder();
    float f=(float)worldborder.getClosestDistance(mc.player);
    double d0=Math.min(worldborder.getResizeSpeed() * (double)worldborder.getWarningTime() * 1000.0D,Math.abs(worldborder.getTargetSize() - worldborder.getDiameter()));
    double d1=Math.max((double)worldborder.getWarningDistance(),d0);
    if ((double)f < d1) {
      f=1.0F - (float)((double)f / d1);
    }
 else {
      f=0.0F;
    }
    float prevVignetteBrightness=lightLevel;
    GlStateManager.disableDepth();
    GlStateManager.depthMask(false);
    GlStateManager.tryBlendFuncSeparate(GlStateManager.SourceFactor.ZERO,GlStateManager.DestFactor.ONE_MINUS_SRC_COLOR,GlStateManager.SourceFactor.ONE,GlStateManager.DestFactor.ZERO);
    if (f > 0.0F) {
      GlStateManager.color(0.0F,f,f,1.0F);
    }
 else {
      GlStateManager.color(prevVignetteBrightness,prevVignetteBrightness,prevVignetteBrightness,1.0F);
    }
    ScaledResolution scaledRes=new ScaledResolution(mc);
    GlStateManager.enableBlend();
    mc.getTextureManager().bindTexture(new ResourceLocation("String_Node_Str"));
    Tessellator tessellator=Tessellator.getInstance();
    BufferBuilder vertexbuffer=tessellator.getBuffer();
    vertexbuffer.begin(7,DefaultVertexFormats.POSITION_TEX);
    vertexbuffer.pos(0.0D,(double)scaledRes.getScaledHeight() * scaledRes.getScaleFactor() * 1D,-90.0D).tex(0.0D,1.0D).endVertex();
    vertexbuffer.pos((double)scaledRes.getScaledWidth() * scaledRes.getScaleFactor(),(double)scaledRes.getScaledHeight() * scaledRes.getScaleFactor(),-90.0D).tex(1.0D,1.0D).endVertex();
    vertexbuffer.pos((double)scaledRes.getScaledWidth() * scaledRes.getScaleFactor(),0.0D,-90.0D).tex(1.0D,0.0D).endVertex();
    vertexbuffer.pos(0.0D,0.0D,-90.0D).tex(0.0D,0.0D).endVertex();
    tessellator.draw();
    GlStateManager.depthMask(true);
    GlStateManager.enableDepth();
    GlStateManager.color(1.0F,1.0F,1.0F,1.0F);
    GlStateManager.tryBlendFuncSeparate(GlStateManager.SourceFactor.SRC_ALPHA,GlStateManager.DestFactor.ONE_MINUS_SRC_ALPHA,GlStateManager.SourceFactor.ONE,GlStateManager.DestFactor.ZERO);
  }
}