Program: 30575
Project: 30575
Buggy source:
public static boolean place(EntityPlayer player,World world){
  MovingObjectPosition hit=RayTracer.reTrace(world,player);
  if (hit == null)   return false;
  BlockCoord pos=new BlockCoord(hit.blockX,hit.blockY,hit.blockZ).offset(hit.sideHit);
  ItemStack held=player.getHeldItem();
  TMultiPart part=null;
  Block blk=null;
  if (held == null)   return false;
  if (held.getItem() instanceof AEBaseItemBlock) {
    AEBaseItemBlock ib=(AEBaseItemBlock)held.getItem();
    blk=Block.getBlockFromItem(ib);
    part=PartRegistry.getPartByBlock(blk,hit.sideHit);
  }
  if (part == null)   return false;
  if (world.isRemote && !player.isSneaking()) {
    Vector3 f=new Vector3(hit.hitVec).add(-hit.blockX,-hit.blockY,-hit.blockZ);
    Block block=world.getBlock(hit.blockX,hit.blockY,hit.blockZ);
    if (block != null && !ignoreActivate(block) && block.onBlockActivated(world,hit.blockX,hit.blockY,hit.blockZ,player,hit.sideHit,(float)f.x,(float)f.y,(float)f.z)) {
      player.swingItem();
      PacketCustom.sendToServer(new C08PacketPlayerBlockPlacement(hit.blockX,hit.blockY,hit.blockZ,hit.sideHit,player.inventory.getCurrentItem(),(float)f.x,(float)f.y,(float)f.z));
      return false;
    }
  }
  TileMultipart tile=TileMultipart.getOrConvertTile(world,pos);
  if (tile == null || !tile.canAddPart(part))   return false;
  if (!world.isRemote) {
    TileMultipart.addPart(world,pos,part);
    world.playSoundEffect(pos.x + 0.5,pos.y + 0.5,pos.z + 0.5,blk.stepSound.func_150496_b(),(blk.stepSound.getVolume() + 1.0F) / 2.0F,blk.stepSound.getPitch() * 0.8F);
    if (!player.capabilities.isCreativeMode) {
      held.stackSize--;
      if (held.stackSize == 0) {
        player.inventory.mainInventory[player.inventory.currentItem]=null;
        MinecraftForge.EVENT_BUS.post(new PlayerDestroyItemEvent(player,held));
      }
    }
  }
 else {
    player.swingItem();
    try {
      NetworkHandler.instance.sendToServer(new PacketMultiPart());
    }
 catch (    IOException e) {
      AELog.error(e);
    }
  }
  return true;
}

Fixed version (ground truth):
public static boolean place(EntityPlayer player,World world){
  MovingObjectPosition hit=RayTracer.reTrace(world,player);
  if (hit == null)   return false;
  BlockCoord pos=new BlockCoord(hit.blockX,hit.blockY,hit.blockZ).offset(hit.sideHit);
  ItemStack held=player.getHeldItem();
  TMultiPart part=null;
  Block blk=null;
  if (held == null)   return false;
  if (held.getItem() instanceof AEBaseItemBlock) {
    AEBaseItemBlock ib=(AEBaseItemBlock)held.getItem();
    blk=Block.getBlockFromItem(ib);
    part=PartRegistry.getPartByBlock(blk,hit.sideHit);
  }
  if (part == null)   return false;
  if (world.isRemote && !player.isSneaking()) {
    Vector3 f=new Vector3(hit.hitVec).add(-hit.blockX,-hit.blockY,-hit.blockZ);
    Block block=world.getBlock(hit.blockX,hit.blockY,hit.blockZ);
    if (block != null && !ignoreActivate(block) && block.onBlockActivated(world,hit.blockX,hit.blockY,hit.blockZ,player,hit.sideHit,(float)f.x,(float)f.y,(float)f.z)) {
      player.swingItem();
      PacketCustom.sendToServer(new C08PacketPlayerBlockPlacement(hit.blockX,hit.blockY,hit.blockZ,hit.sideHit,player.inventory.getCurrentItem(),(float)f.x,(float)f.y,(float)f.z));
      return true;
    }
  }
  TileMultipart tile=TileMultipart.getOrConvertTile(world,pos);
  if (tile == null || !tile.canAddPart(part))   return false;
  if (!world.isRemote) {
    TileMultipart.addPart(world,pos,part);
    world.playSoundEffect(pos.x + 0.5,pos.y + 0.5,pos.z + 0.5,blk.stepSound.func_150496_b(),(blk.stepSound.getVolume() + 1.0F) / 2.0F,blk.stepSound.getPitch() * 0.8F);
    if (!player.capabilities.isCreativeMode) {
      held.stackSize--;
      if (held.stackSize == 0) {
        player.inventory.mainInventory[player.inventory.currentItem]=null;
        MinecraftForge.EVENT_BUS.post(new PlayerDestroyItemEvent(player,held));
      }
    }
  }
 else {
    player.swingItem();
    try {
      NetworkHandler.instance.sendToServer(new PacketMultiPart());
    }
 catch (    IOException e) {
      AELog.error(e);
    }
  }
  return true;
}