Program: 30489
Project: 30489
Buggy source:
@SubscribeEvent public void playerInteract(final PlayerInteractEvent event){
  if (event instanceof PlayerInteractEvent.RightClickEmpty && event.getEntityPlayer().worldObj.isRemote) {
    final RayTraceResult mop=Platform.rayTrace(event.getEntityPlayer(),true,false);
    final Minecraft mc=Minecraft.getMinecraft();
    final float f=1.0F;
    final double d0=mc.playerController.getBlockReachDistance();
    final Vec3d vec3=mc.getRenderViewEntity().getPositionEyes(f);
    if (mop != null && mop.hitVec.distanceTo(vec3) < d0) {
      final World w=event.getEntity().worldObj;
      final TileEntity te=w.getTileEntity(mop.getBlockPos());
      if (te instanceof IPartHost && this.wasCanceled) {
        event.setCanceled(true);
      }
    }
 else {
      final ItemStack held=event.getEntityPlayer().getHeldItem(event.getHand());
      final IItems items=AEApi.instance().definitions().items();
      boolean supportedItem=items.memoryCard().isSameAs(held);
      supportedItem|=items.colorApplicator().isSameAs(held);
      if (event.getEntityPlayer().isSneaking() && held != null && supportedItem) {
        NetworkHandler.instance.sendToServer(new PacketClick(event.getPos(),event.getFace(),0,0,0,event.getHand()));
      }
    }
  }
 else   if (event instanceof PlayerInteractEvent.RightClickBlock && event.getEntityPlayer().worldObj.isRemote) {
    if (this.placing.get() != null) {
      return;
    }
    this.placing.set(event);
    final ItemStack held=event.getEntityPlayer().getHeldItem(event.getHand());
    if (place(held,event.getPos(),event.getFace(),event.getEntityPlayer(),event.getHand(),event.getEntityPlayer().worldObj,PlaceType.INTERACT_FIRST_PASS,0) == EnumActionResult.SUCCESS) {
      event.setCanceled(true);
      this.wasCanceled=true;
    }
    this.placing.set(null);
  }
}

Fixed version (ground truth):
@SubscribeEvent public void playerInteract(final PlayerInteractEvent event){
  if (event.getHand() != EnumHand.MAIN_HAND) {
    return;
  }
  if (event instanceof PlayerInteractEvent.RightClickEmpty && event.getEntityPlayer().worldObj.isRemote) {
    final RayTraceResult mop=Platform.rayTrace(event.getEntityPlayer(),true,false);
    final Minecraft mc=Minecraft.getMinecraft();
    final float f=1.0F;
    final double d0=mc.playerController.getBlockReachDistance();
    final Vec3d vec3=mc.getRenderViewEntity().getPositionEyes(f);
    if (mop != null && mop.hitVec.distanceTo(vec3) < d0) {
      final World w=event.getEntity().worldObj;
      final TileEntity te=w.getTileEntity(mop.getBlockPos());
      if (te instanceof IPartHost && this.wasCanceled) {
        event.setCanceled(true);
      }
    }
 else {
      final ItemStack held=event.getEntityPlayer().getHeldItem(event.getHand());
      final IItems items=AEApi.instance().definitions().items();
      boolean supportedItem=items.memoryCard().isSameAs(held);
      supportedItem|=items.colorApplicator().isSameAs(held);
      if (event.getEntityPlayer().isSneaking() && held != null && supportedItem) {
        NetworkHandler.instance.sendToServer(new PacketClick(event.getPos(),event.getFace(),0,0,0,event.getHand()));
      }
    }
  }
 else   if (event instanceof PlayerInteractEvent.RightClickBlock && !event.getEntityPlayer().worldObj.isRemote) {
    if (this.placing.get() != null) {
      return;
    }
    this.placing.set(event);
    final ItemStack held=event.getEntityPlayer().getHeldItem(event.getHand());
    if (place(held,event.getPos(),event.getFace(),event.getEntityPlayer(),event.getHand(),event.getEntityPlayer().worldObj,PlaceType.INTERACT_FIRST_PASS,0) == EnumActionResult.SUCCESS) {
      event.setCanceled(true);
      this.wasCanceled=true;
    }
    this.placing.set(null);
  }
}