Program: 27527
Project: 27527
Buggy source:
public static ChangeBlockEvent.Place createChangeBlockEventPlace(BlockEvent.MultiPlaceEvent forgeEvent){
  final net.minecraft.world.World world=forgeEvent.getWorld();
  if (world.isRemote) {
    return null;
  }
  ImmutableList.Builder<Transaction<BlockSnapshot>> builder=new ImmutableList.Builder<Transaction<BlockSnapshot>>();
  for (  net.minecraftforge.common.util.BlockSnapshot blockSnapshot : forgeEvent.getReplacedBlockSnapshots()) {
    final BlockPos snapshotPos=blockSnapshot.getPos();
    BlockSnapshot originalSnapshot=((IMixinBlockSnapshot)blockSnapshot).createSpongeBlockSnapshot();
    BlockSnapshot finalSnapshot=((World)world).createSnapshot(snapshotPos.getX(),snapshotPos.getY(),snapshotPos.getZ());
    builder.add(new Transaction<>(originalSnapshot,finalSnapshot));
  }
  final PhaseTracker phaseTracker=PhaseTracker.getInstance();
  final PhaseData data=phaseTracker.getCurrentPhaseData();
  User owner=data.context.getOwner().orElse(null);
  User notifier=data.context.getNotifier().orElse(null);
  EntityPlayer player=forgeEvent.getPlayer();
  if (SpongeImplHooks.isFakePlayer(player)) {
    Sponge.getCauseStackManager().addContext(EventContextKeys.FAKE_PLAYER,EntityUtil.toPlayer(player));
  }
 else   if (Sponge.getCauseStackManager().getCurrentCause() == null) {
    Sponge.getCauseStackManager().pushCause(player);
  }
  if (owner != null) {
    Sponge.getCauseStackManager().addContext(EventContextKeys.OWNER,owner);
    if (Sponge.getCauseStackManager().getCurrentCause() == null) {
      Sponge.getCauseStackManager().pushCause(owner);
    }
  }
 else {
    Sponge.getCauseStackManager().addContext(EventContextKeys.OWNER,(User)player);
    if (Sponge.getCauseStackManager().getCurrentCause() == null) {
      Sponge.getCauseStackManager().pushCause(player);
    }
  }
  if (notifier != null) {
    Sponge.getCauseStackManager().addContext(EventContextKeys.NOTIFIER,notifier);
  }
  return SpongeEventFactory.createChangeBlockEventPlace(Sponge.getCauseStackManager().getCurrentCause(),builder.build());
}

Fixed version (ground truth):
private static ChangeBlockEvent.Place createChangeBlockEventPlace(BlockEvent.MultiPlaceEvent forgeEvent){
  final net.minecraft.world.World world=forgeEvent.getWorld();
  if (world.isRemote) {
    return null;
  }
  ImmutableList.Builder<Transaction<BlockSnapshot>> builder=new ImmutableList.Builder<>();
  for (  net.minecraftforge.common.util.BlockSnapshot blockSnapshot : forgeEvent.getReplacedBlockSnapshots()) {
    final BlockPos snapshotPos=blockSnapshot.getPos();
    BlockSnapshot originalSnapshot=((IMixinBlockSnapshot)blockSnapshot).createSpongeBlockSnapshot();
    BlockSnapshot finalSnapshot=((World)world).createSnapshot(snapshotPos.getX(),snapshotPos.getY(),snapshotPos.getZ());
    builder.add(new Transaction<>(originalSnapshot,finalSnapshot));
  }
  final PhaseTracker phaseTracker=PhaseTracker.getInstance();
  final PhaseData data=phaseTracker.getCurrentPhaseData();
  User owner=data.context.getOwner().orElse(null);
  User notifier=data.context.getNotifier().orElse(null);
  EntityPlayer player=forgeEvent.getPlayer();
  if (SpongeImplHooks.isFakePlayer(player)) {
    Sponge.getCauseStackManager().addContext(EventContextKeys.FAKE_PLAYER,EntityUtil.toPlayer(player));
  }
 else   if (!Sponge.getCauseStackManager().getCurrentCause().contains(player)) {
    Sponge.getCauseStackManager().pushCause(player);
  }
  if (owner != null) {
    Sponge.getCauseStackManager().addContext(EventContextKeys.OWNER,owner);
    if (!Sponge.getCauseStackManager().getCurrentCause().contains(owner)) {
      Sponge.getCauseStackManager().pushCause(owner);
    }
  }
 else {
    Sponge.getCauseStackManager().addContext(EventContextKeys.OWNER,(User)player);
    if (!Sponge.getCauseStackManager().getCurrentCause().contains(player)) {
      Sponge.getCauseStackManager().pushCause(player);
    }
  }
  if (notifier != null) {
    Sponge.getCauseStackManager().addContext(EventContextKeys.NOTIFIER,notifier);
  }
  return SpongeEventFactory.createChangeBlockEventPlace(Sponge.getCauseStackManager().getCurrentCause(),builder.build());
}