Program: 169627
Project: 169627
Buggy source:
/** 
 * Mainly updates data used by the client renderer(e.g. Metadata)
 */
public void updateRenderState(){
  int meta=worldObj.getBlockMetadata(xCoord,yCoord,zCoord);
  int antennaParts=connections.size();
  if (antennaParts > 3) {
    if (meta != 3) {
      worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,3,3);
    }
  }
 else   if (antennaParts == 2) {
    if (connections.get(ForgeDirection.UP) != null && connections.get(ForgeDirection.DOWN) != null) {
      TileEntity above=connections.get(ForgeDirection.UP);
      TileEntity bellow=connections.get(ForgeDirection.DOWN);
      boolean found=false;
      if (above instanceof TileAntennaPart && bellow instanceof TileAntennaPart) {
        boolean connectionA=((TileAntennaPart)above).connections.get(ForgeDirection.UP) != null && ((TileAntennaPart)above).connections.get(ForgeDirection.DOWN) != null;
        boolean connectionB=((TileAntennaPart)bellow).connections.get(ForgeDirection.UP) != null && ((TileAntennaPart)bellow).connections.get(ForgeDirection.DOWN) != null;
        if (connectionA && !connectionB || connectionB && !connectionA) {
          found=true;
          if (!found && meta != 4) {
            worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,4,3);
          }
        }
      }
      if (!found && meta != 1) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,1,3);
      }
    }
 else     if (connections.get(ForgeDirection.EAST) != null && connections.get(ForgeDirection.WEST) != null) {
      if (meta != 6) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,6,3);
      }
    }
 else     if (connections.get(ForgeDirection.NORTH) != null && connections.get(ForgeDirection.SOUTH) != null) {
      if (meta != 7) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,7,3);
      }
    }
 else     if (meta != 3) {
      worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,3,3);
    }
  }
 else   if (antennaParts == 1) {
    if (connections.get(ForgeDirection.DOWN) != null) {
      if (meta != 5) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,5,3);
      }
    }
 else     if (connections.get(ForgeDirection.EAST) != null || connections.get(ForgeDirection.WEST) != null) {
      if (meta != 6) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,6,3);
      }
    }
 else     if (connections.get(ForgeDirection.NORTH) != null || connections.get(ForgeDirection.SOUTH) != null) {
      if (meta != 7) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,7,3);
      }
    }
  }
}

Fixed version (ground truth):
/** 
 * Mainly updates data used by the client renderer(e.g. Metadata)
 */
public void updateRenderState(){
  int meta=worldObj.getBlockMetadata(xCoord,yCoord,zCoord);
  int antennaParts=connections.size();
  if (antennaParts > 3) {
    if (meta != 3) {
      worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,3,3);
    }
  }
 else   if (antennaParts == 2) {
    if (connections.get(ForgeDirection.UP) != null && connections.get(ForgeDirection.DOWN) != null) {
      TileEntity above=connections.get(ForgeDirection.UP);
      TileEntity bellow=connections.get(ForgeDirection.DOWN);
      boolean found=false;
      if (above instanceof TileAntennaPart && bellow instanceof TileAntennaPart) {
        boolean connectionA=((TileAntennaPart)above).connections.get(ForgeDirection.UP) != null && ((TileAntennaPart)above).connections.get(ForgeDirection.DOWN) != null;
        boolean connectionB=((TileAntennaPart)bellow).connections.get(ForgeDirection.UP) != null && ((TileAntennaPart)bellow).connections.get(ForgeDirection.DOWN) != null;
        if (connectionA && !connectionB || connectionB && !connectionA) {
          found=true;
          if (found && meta != 4) {
            worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,4,3);
          }
        }
      }
      if (!found && meta != 1) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,1,3);
      }
    }
 else     if (connections.get(ForgeDirection.EAST) != null && connections.get(ForgeDirection.WEST) != null) {
      if (meta != 6) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,6,3);
      }
    }
 else     if (connections.get(ForgeDirection.NORTH) != null && connections.get(ForgeDirection.SOUTH) != null) {
      if (meta != 7) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,7,3);
      }
    }
 else     if (meta != 3) {
      worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,3,3);
    }
  }
 else   if (antennaParts == 1) {
    if (connections.get(ForgeDirection.DOWN) != null) {
      if (meta != 5) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,5,3);
      }
    }
 else     if (connections.get(ForgeDirection.EAST) != null || connections.get(ForgeDirection.WEST) != null) {
      if (meta != 6) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,6,3);
      }
    }
 else     if (connections.get(ForgeDirection.NORTH) != null || connections.get(ForgeDirection.SOUTH) != null) {
      if (meta != 7) {
        worldObj.setBlockMetadataWithNotify(xCoord,yCoord,zCoord,7,3);
      }
    }
  }
}